Hi, guys and gals, Gashadokuro here.

I’ve been on this site for quite some time in which I’ve grown quite a lot as a writer. This does not just mean the writing style, but also plot and characters. Naturally I can’t say I am perfect, but I can see how far I’ve come. Though that did have the unfortunate side effect of me not being able to enjoy some stories anymore that I liked earlier, as I now have a lot stricter sense for what I consider good writing. But I’d say the trade-off was worth it.

I’ve also finished my first real story after literally years, which made me appreciate just how much effort real authors have to put into their stories. It also told me something really important:

I won’t be able to write all the stories, I want to. I have so many ideas for stories, but I will never be able to see them all come to life, because I won’t have the time for them, literally. I am not like the people who can write a new chapter a day, I need around a month for that. So I am really not just exaggerating when I declare it impossible.

But since I already had these idea, with some of them having quite the potential in my opinion, I decided to put them up as some kind of challenges in hopes of someone else maybe finding the inspiration and time to realize them.

And I say “some kind of” challenges, because I have nothing against someone taking the core idea and write a story with that, if the details or restrictions would get in the way of their inspiration. Though the restrictions are generally there for a reason. Namely that I think a story like that without these would not be a good one, or at last not one I would like. You disagree? Then you’re welcome to try to prove me wrong.

Nevertheless, no matter what you decide on, if you take up a challenge or if you just get inspired by one, please notify me and note in your story where you’ve got the idea from. The first is so that I can see the idea come to life, while the second one is so that others might decide to look up the challenges, too, and maybe get inspirations of their own.

Edit (11-06-2019): After getting down to it, I’ve realized that even a single story would probably be more than I can complete on my own. I just don’t have the time for something like that anymore. I’ve gotta work to live and can’t use up so much of my day anymore for fanfiction, especially if at some point I want to make an original story. But I’ve got so many ideas for my new story “Heart of Akasha” that I don’t want to just give up on it. That is why I am looking for people to help me in the forum “Heart of Akasha Discussions”. There you can help me with a lot of different stuff, large and small. Heck, you might even have fun thinking of anime characters fitting for Nobodies or Hero Union members after reading about my examples. Just take a look if you are interested.

Challenges (or Fanfictions ideas I likely won’t be going to write)

Overview (normal/Crossover)

Absolute Duo (0/1); Assassination Classroom (0/1); Chuunibyou Demo Koi Ga Shitai (0/1); Code Lyoko (2/0); Daily Life with Monster Girls (0/1); Fate Series (1/3); Iris Zero (0/1); Kantai Collection (1/0); Naruto (2/0); Nurarihyon no Mago (0/1); Percy Jackson (0/1); Shingeki no Kyoujin (0/1); Soul Eater (1/0); Sword Art Online (0/2); Tsukihime (0/3); Yumekui Merry (0/2)

Absolute Duo

The Lone Hero (X Fate series)

Summary:
Emiya Shirou, survivor of the Fuyuki Fire, was accepted into the school with a pair of beautiful black and white [Falchion] as [Blaze]. But what they didn’t knew, he was a [Deviation] (name not mandatory), someone who was able to understand any [Blaze] he sees and use it himself. But sometimes even a hero needs a partner.

Optional:
If you want you can add other characters from the Fate series as students. I highly recommend introducing also another orphan named “Angra Mainyu” who is also something along the lines of an [Abnormality] with two certain sword-breakers as [Blaze] because let’s face it, someone with weapons designed to break other weapons in a world were you transform your soul into a weapon should get rather interesting. Especially if you decide to make Angra Mainyu Shirou’s partner since interactions between them should be really interesting.

Restrictions:
Don’t cut out any of the [Irregular] or [Exceptions] because they are going to probably going to be the only ones that Shirou won’t be able to copy.
The story is called Absolute Duo for a reason and so Shirou has to get a partner. And no matter who decide that person to be, an OC or someone from Fate or Absolute Duo, he would have to learn to work together sooner or later.

Remember:
This is not a Crossover with Fate Mechanics or someone of the nasuverse thrown into the Absolute Duo Universe. This is like an alternative universe of Absolute Duo where there exist a person named Emiya Shirou (and Angra Mainyu) who has abilities and personalities similar to the ones known in the nasuverse. So, Shirou’s swords can have similar abilities in Absolute Zero, but the strength should be toned down a bit. I doubt anything in the Absolute Duo-universe can hold a candle to an actual Noble Phantasm.

Assassination Classroom

Unusual New Normal Students (X-Over)

Summary:
Because of… circumstances they had to leave their old school and are now students on the Kunugigaoka Junior High School. But after some secrets were exposed they wind up in the End-Class, helping their classmates try to kill their teacher.

Details:
Some stories are better suited for fanfiction than others. I also enjoy stories of school life with supernatural elements in them. But because they are usually more focused on the interactions between the people it is difficult to make a lot of good and different fanfiction about them or fighting-based fanfiction in general without completely disregarding the original feel of the canon story.
Assassination Classroom, however, turns a class of normal students (with the odd-ones out) into capable assassins without taking away their humanity or changing their behavior drastically. They are just like normal students, albeit confident ones but the only thing that really tells you something is odd about them is the fact that they develop a bit of bloodlust every time someone mentions “kill” or “die” without meaning it literally. But even then they never kill normal people and only use it as means of intimidation.
In other words, it’s the best environment for a character from a non-violent background to become a capable fighter/assassin.

Optional:
The time that the transfer happens is not set though it shouldn’t be too late so that the new students can interact and create bonds with the class.
The number of new students isn’t set either, but you shouldn’t make it too large (I would prefer 1 to 3) because that would be more like a second smaller class inside the original one, especially if the new students all already know each other.
Now this is just a personal preference, but I would really like for the new students to have supernatural abilities.

Restrictions:
The new students have to be characters from other franchises. All of the new students together should not be stronger than Itona or even capable of killing Koro-Sensei on their own. They should still have to work together with the others for their assassination.
Just like the original students of the class, the transfer students should not have his behavior change too drastically, just enough to become a capable assassin while still being a child.
Any person with the ability to read thoughts or gather information should not have them work on Koro-sensei directly.

Remember:
No matter how nice Koro-sensei is, he does threaten to blow up the earth, if he isn’t killed. On the other hand, he cares for all of his students and tries to help them with their problems.

Chuunibyou Demo Koi Ga Shitai

The Real Summoning (X-Over)

Summary:
What happens when people with eight-grader syndrome manage to utilize real magic by chance and summon a person from another world into their one?

Details:
Ever wondered what happens when one of the delusions in Chuunibyou suddenly started to turn out real? When Rikka and her club once again played with the LED-decorated magic circle, their complete lives turned upside down as suddenly a person from another world (a different franchise) appeared in the room. Now they know that supernatural abilities exist at last in some form and are stuck with a more or less unpleased person from another universe, opposite to them authentically capable of supernatural feats.

Optional:
Who exactly the summoned person is, is left up to you, as long as he is not an OC and has some form of supernatural ability, no matter how small. But it might be interesting for the person to have some non-human features or to have no clue of this worlds customs.
It is also not set when in the story this happens so, the people of the club (or even the club name) are not set.
You can add organizations, individual people or beings who know of or use magic which they can encounter by stumbling upon them as they search for a way to send the summoned back or for them to get contacted by such people because the summoned acted too conspicuous in public.

Restrictions:
No canon character from Chuunibyou must be capable of using a supernatural ability. Only the people who where present to the summoning are allowed to show aptitude for the supernatural but only after meeting a real magician.
Any real magicians or other supernatural entities must have different abilities than those made up in Chuunibyou-canon. And they should not make contact with the canon cast until they have at last somewhat managed to settle in the summoned. I don’t want you to take the easy way out and have issues like place of residence sorted out “with magic”.
No killing. Fighting should be kept to a minimum and should have only consequences on a limited scale. Nothing on city-destroying level. The focus of this story should be how the Chuunibyou-cast deals with the situation and not how powerful the summoned is. This is also why I don’t want the summoned to have more abilities than in his canon. It would just be distracting.
If you plan for the summoned to be one of the “bad guys”, his actions have to be restricted by the summoning so that he does not cross his summoner or kill people. The personality itself should not be changed.

Remember:
Seeing some real supernatural effects is definitively have some effects on the chuunibyou. And those do not necessarily have to be good.
Depending on who was summoned, he might hold it against the chuunibyou-cast and/or wants to find a way to go back. Though the latter is probably holding true for the majority.

Code Lyoko

Code Lyoko: Teacher Edition

Summary:
How the teachers of the Kadic Academy became Lyoko Warriors.

Details:
At the end of the second season (episode 52) the Lyoko Warriors decide they are in way over their head. And since one of the reasons for shutting down Lyoko now has become a reason for keeping it, they decide to confine in a teacher. One thing leads to another and now all the teacher of Kadic Academy know about Lyoko, helping the students in their fight against X.A.N.A.

Optional:
If you add the principal Mr. Delmas to the people knowing about Lyoko is up to you.
How many of the teachers become active Lyoko Warriors is up to you but unless you have a valid reason why one teacher should not be in the know, I want the teachers to have enough trust in each other to tell each other about the problem.

Restrictions:
Code Lyoko should not be shut down.
Beyond the teachers of Kadic Academy no adult should be confined in the secret. The more people know a secret, the more likely it is for one to betray them. So while the teachers have known each other for some time and since to their close proximity often more than not even personally, the same cannot be said about others. The exceptions are the parents of the Lyoko Warriors, who can be told about the secret if they manage to keep the secret without knowing about “Return to the Past”.
I definitely do not want any secret agents to be let in on the secret. I mean, who knows who they are really working for? They could be terrorists or war hawks trying to get a super-weapon for all they know. Even if they are working for the government without any evil intention, they still could decide to let some people vanish because the secret is too dangerous.

Remember:
Aelita is still the only one capable of shutting down the towers.
I expect a lot of “This is dangerous”-reactions from the teachers regarding the students venture into Lyoko. Those can be refuted by (a) they are already on X.A.N.A.’s hit-list, (b) the fact that during an attack Lyoko is more often than not less dangerous than the real world for any Lyoko Warrior and (c) the students have more experience fighting on Lyoko than the teachers. So while there might be some natural talents among the teachers, others would have to train first.
While saving the world gives one more leeway with homework and missing classes, I expect a lot “Saving the world is no excuse for slacking in your studies”-moments.
Also, ego trips should be heavenly discouraged by adults.
On another note, can you imagine the teachers reactions to the fact that thanks to “Return to the Past” some students already know test questions?
As the voices of reason, the teachers should be skeptical to any experiments Jeremy would try and, if Jeremy can convince them that the experiment is necessary, volunteer first before allowing it to be tried on the students.
Since they now have more people to help, I would be really disappointed if the events happened the same as canon. Especially those related to the Scyphozoa.

Cybernetic Warfare

Summary:
Franz Hopper wasn’t the only one to create a virtual world using a supercomputer. In fact, all over the world people have created visual worlds… to wage war.

Details:
If one person can do something who’s to say that a second won’t? And since militaristic organizations are usually the first one to develop new technology whose to say they won’t be used for war? I am not talking about the victory being decided by online fights and the loser’s organization hissing the white flag. No, but since the first season is all about trying to find a way to materialize someone from Lyoko, so what if they knew how to, with their online abilities. I think everyone can imagine that having someone with the abilities of the Lyoko Warriors on earth, would give them a lot of military might. Especially if those people only rematerialize in the scanners after they’ve been killed.
However, since not only one organization is using this method, they don’t use their materialized warriors and go to war just yet. Instead they use their virtualized bodies, travel through the world wide web to reach the other virtual worlds first, materialize there and destroy the supercomputer of the other worlds, taking away the others’ methods of materialization.
The Lyoko Warriors who have their hands full with X.A.N.A. are now thrown into this mess of a war.

Optional:
The timeframe that the Lyoko Warriors meet with the soldiers from the other organizations is not set though I would suggest sometimes in the fourth season (episode 66 onwards).
Not all organizations have to be their enemies. One or two of them could help them, even against X.A.N.A..
On the other hand it’s also quite possible for X.A.N.A. to make a truce with the Lyoko Warriors until they’ve dealt with all the other threats.

Restrictions:
It would be too easy if just getting to another world allows them to materialize on the location of the corresponding supercomputer. Like X.A.N.A. they should need to take control of a tower first and have to defend it.
X.A.N.A. is to be the only artificial intelligence working towards world domination.
Only the Lyoko Warriors should have the “Return to the Past” and only those connected to Lyoko should be able to remember what happened. The Lyoko Warriors wouldn’t get any pause if people found out about them being able to manipulate time.
I do not want the Lyoko Warriors to be completely overshadowed by people from another organization, especially if they happen to ally with them. The Lyoko Warriors should be able to hold their own in fights. If they have to team up with someone around their level to defeat a more powerful enemy that’s okay.
It could be possible for someone to materialize near their supercomputer and then travel through the real world to the others locations but since most of the story should be online, I want all the supercomputers to have some really strong defenses that prevent someone from figuring out their real-world locations through online data transfer. However, if someone where figure out the locations through things like the position of stars and gossip that would be a different story.

Remember:
Since all virtual worlds are created by different people they should all look different.
X.A.N.A. does not try the same thing twice but humans might be different. Sometimes using the same strategy again is actually a valid tactic.
A “Return to the Past” would just sent any attackers back. If they don’t remember what happened, they have no reason not to attack again. But it would give the Lyoko Warriors time to prepare and information on the enemies’ capabilities, maybe even allowing a preemptive strike.
The Lyoko Warriors are a rather small group that still has some other things to do. The others can have a lot more people who have nothing else to do. One thing the Lyoko Warriors can have work for them is Quality vs. Quantity. They could also have a more effective supercomputer. Or Jeremy could program more superpowers.

Fate series

Fate Everyday Heroes

Summary:
At the end of the 4th Holy Grail War, Angra Mainyu used up nearly all of the prana from the Holy Grail for the fire. This would not have been a problem if Kiritsugu didn’t positioned explosives at the laylines to disrupt them in ten years. So, Angra Mainyu has no chance but to activate the 5th Grail War a bit earlier. However, since he has not enough prana gathered, he can only manage seven weaker irregular classes.

Optional:
You can either chose some historical characters or characters from other media. Preferable those that usually would have no chance of being summoned in the Holy Grail War.
Ideas for possible Servant classes are Gunner, Idol, Butler, Mascot, Author, Carpenter, Fool, Inventor, Painter, and Musician.

Restrictions:
Do not use any of the standard classes or powerful irregular classes like Saver or Ruler.
Gilgamesh mustn’t win in the end and the Grail has to be destroyed.

Remember:
These irregular classes should be weak compared to the standard ones, but may have a Noble Phantasm that is good in favorable circumstances.

Iris Zero

Those Cursed Eyes (X Tsukihime)

Summary:
When a new transfer student came into their class, everybody was of course exited. That is, until someone asked what Iris he had and he proclaimed, he had none. From that moment onward, he was an object of bullying. However, Asahi Yuki could see the truth: He was not honest! Just what kind of Iris did this guy had that he would rather be seen as an Iris Zero and how could she and her friends help him accept his?

Details:
Shiki Tohno, the owner of the Mystic Eyes of Death Perception in another world, in this world is just another one of the 99% of children with the supernatural power called Iris. However, the abilities, are the same. Without anybody like Aozaki to guide him, he becomes someone hating his Iris which only use seems to be killing things and keeps his distance to people so that they do not find out and/or he might kill them.
Now put him into the vicinity of Toru Mizushima, whose purpose seems to be helping other people get over the fear of their Irises and his friends who cannot leave other people alone and show how this plays put.

Optional:
If you want you can make this as Sequel to the manga and throw in some more people with Iris problems in there afterwards. Maybe even from some other franchises.

Restrictions:
The Irises are the only supernatural aspect of Iris Zero so I do not want other supernatural abilities or entities to make an entrance.
Irises are only information-gathering abilities. So, I do not want to see things like Petrification or Telekinesis.

Remember:
The focus in the story is on Iris Zero. So combat is only present in the rarest of cases and does not go over some school scrabbles.

Kantai Collection

Abyssmal Admiral

Summary:
They couldn’t believe it. They actually got the opportunity to go to the world of his favorite game with all the waifus. They couldn’t wait to become their admiral and guide them in defending humanity. They wondered what their starter was going to be… why was there a Tsu-Class welcoming them?

Details:
A self-insert with a twist. When the main character got the offer to go into the world of Kancolle and work as an admiral, they, being a huge fan of the franchise, took not too long to accept. Unfortunately their role was not to be an admiral for the Fleet Girls of a naval base, but instead to be an admiral of the Abyssal Fleet with an Abyssal base. In other words, kill all their waifus. That wasn’t what they signed up for! Unfortunately they were still very human and being the admiral was the only thing that stopped the Abyssals from killing them.
So, either they were going to accept their death or walk a fine line between being a bad admiral and still being useful enough to keep around. And, well, if they chose the first option, this wouldn’t really be a story now would it?

Optional:
The starter doesn’t really have to be a Tsu-Class. I just looked at a comparably weak yet still humanoid Abyssal for the starter. Someone with more detailed knowledge can easily find a better starter.
Considering the appearance of the Abyssals, it wouldn’t be strange for the MC to find some waifus inside his own base and thus get reluctant to send them off to their deaths. Or, in general, they could find some they favor over others, for example, a destroyer with dog-like behavior.

Restrictions:
No giving up on saving as many Fleet Girls as possible, at last not permanently. I don’t like reading stories were the MC has fun eradicating mankind (or his own human-flawed race) and I especially dislike it if they pretend they don’t when it is obvious they do. Temporarily it is acceptable for the MC to get cold feet – Abyssals are quite scary – but I still expect them to at last try to do the right thing.

Remember:
Kantai Collection is a bit fuzzy on what actually is canon and what not. So you should just work with your own understandings of canon but be careful not to contradict yourself.

Naruto

Because I am a Nara

Summary:
“How did you knew Naruto is the host of the Kyuubi?” “Because I am a Nara.”
”How did you knew Mizuki was a traitor?” “Because I am a Nara.”
”How did you knew Orochimaru was in the Forest of Death?” “Because I am a Nara.”
Because knowing the past can save the future.

Details:
Besides their clan techniques, the Nara have one more secret, one that has been guarded furiously by them, a dormant Kekkei Genkai, not having been seen since who knows how long. An ability that lets it user see the “Shadows of the Past”, in other words, the history of the people he meets, from their moment of birth to this day. Nara Shikamaru, the offspring of Nara Shikaku was born with it.

Optional:
You can make this ability either a Kekkei Genkai or a Hiden that only few are compatible with, but Shikamaru should be the only one with this ability in some generations.
You can make restrictions for the use of this ability. Maybe he gets only the information of the people whose shadows he steps in.

Restrictions:
The potential of this ability is so great, it should be kept secret with only a few knowing of it like maybe the Hokage. Shikamaru himself wouldn’t want for certain people to find out (like Danzo).
This ability only shows him their past from an third-point of view. So he only knows what they did or what happened to them, not their thoughts at this moment.
He mustn’t get any other additional abilities other than reading people’s past. With this ability, the shadow manipulation and his intelligence that is already one hell of a combination.

Remember:
This ability does not only gives him knowledge about their skills, techniques and plans, it also gives him insight into their troubles and motivations. He would get to know each one of them like a close friend. So either he is going to be completely heartless or not capable of killing even one person unless those people are like Gato or Hidan.

Freaky Friday Timetravel

Summary:
They came back from the future to prevent all the bad things to happen and save all their friends. But not only have they to deal with being stuck in a child’s body, they have to deal with getting stuck in someone else’s child’s body.

Details:
There are a lot of Timetravel-fanfics in which someone ends up back in time either traveling with his body or only with his soul, making him turn up in his old body. But I have yet to see a fanfiction where they end up in someone else’s body.
So, I had this idea: One or two people from the Allied Shinobi Forces who want to save their friends and the world while they are at it travel back in time at the end of the lost Fourth Shinobi War. But something goes wrong and instead in their old body they end taking the place of someone else of the Konoha Twelve and have now to cope with it. The point in time to which they are sent back should be before the Chuunin exam, so that they actually can amount to something.

Optional:
I am being rather vague with this one on purpose, since depending on which characters you chose, this one can turn out completely different. But if I had to name a favorite, it would be Shikamaru, the genius in Naruto, the power house’s body.

Restrictions:
No getting powers out of nowhere. They already have knowledge about their old techniques and can get those of the person whose body they are inhabiting.
Only those not from Konoha are allowed to being back more abilities than they had in canon and only one of them is allowed to be slightly stronger than those they knew in canon.
No Romance for the time travelers for the duration of the story except between each other. They have a body that is a lot younger than their mind. So, the only ones they could actually date at this age is the other time traveler. This does not stop other characters from falling for the time traveler, though.

Remember:
Kekkei Genkai can only be used by those that have the necessary body. So, Sasuke would not be able to use Sharingan in Shikamaru’s body. But Shikamaru could use his clan techniques while in Sasuke’s body.
All ninjutsu need an amount and control over chakra to activate. This is especially going to be crucial if you put someone with naturally low chakra into a body with a lot chakra, making his control messy, or someone with naturally a lot chakra into a body with low chakra, making him easily pass out from chakra exhaustion when he tries to fight like usual.

Nurarihyon no Mago

Daily Life with Yokais (X Daily Life with Monster Girls)

Summary:
The existence of Yokai has been made public and now the world is in uproar. To prove that not all Yokai are bad the Nura clan makes a deal with the Japanese government to send members of their clan to live with normal humans. Now volunteers from both sides live together in the same house, going through normal everyday life while dealing with the occasional human or Yokai fanatics.

Details: While I quite enjoy the funny antics of the cast in Daily Life with Monster Girls, you could do so much more with the premise of the story. So, I had the idea for this crossover. Now instead of love-craving girls we get Yakuza-members on a mission. Not that those can’t fall in love later on in the right circumstances. But their first and foremost priority is to convince humans of not all Yokai being bad.

Optional:
While the setting of Nurarihyon no Mago is a lot more serious than Daily Life with Monster Girls, it doesn’t mean you can’t write a humorous story of daily life interactions between human and Yokai unfamiliar with each other. It all depends on which characters you chose both as hosts and tenants. You can decide on whether you want to focus more on the daily life or a peace-keeping squad like M.O.N. Who you chose is also ultimately up to you. You can even create OC, maybe even other Yokai from all over the world who like Rikuo’s policy or switch the order around, making a Yokai the host and the tenant a human.
Restrictions:
Keep the numbers of characters per household reasonable. The numbers of willing Yokai are way lower than that of monsters in Monster Musume so things like the canon harem would had to have really good explanations for them to happen.

Remember:
Opposite to the monster girls, Yokai are pretty much adapted to living in human society. That means that the Cultural Exchange Program only purpose is to make humans accept Yokai. On the other hand this also means that human have a bigger reason to initially distrust Yokai as it is one thing to accept a race who is obviously different but another to accept a race of people who can pass themselves as human whenever they want to.
In Daily Life with Monsters Girls monsters are not allowed to harm human and vice versa. Considering that the Nura clan wants to reassure humans, there should be a similar rule. However, this should be a lot more detailed than the canon one, allowing for more leeway in certain situations considering that the Nura clan are Yakuza and wouldn’t restrict themselves like the canon cast. The same goes for humans, since the number of cooperative Yokai is way lower than monsters.
If you put in canon monsters from Monster Monsume, don’t forget to “yokaify” them, meaning the ability to pretend to be humans, their personal “Fear” and so on.

Percy Jackson

Of Different Faith (X Tsukihime)

Summary:
Being a man of God did not automatically made him deny the existence of other deities. Though in his mind they were nothing compared to the almighty Lord. However, he did thought that they had all lost their power at the end of the age of gods and not just hid themselves from the ever-growing will of humanity in a world different from the moonlit one.

Details:
A member of the Holy Church (Type Moon-version) is asked to investigate the rumors of an Holy Relic in America only for him to witness some teenagers getting attacked by a member of the Phantasmal Species. After helping them finishing off the monster he finds out that (at last some of them) are actually the offsprings of Greek gods and, since he can see past the mist that the gods created to hide themselves from Alaya and anyone having to do with it, has to be one himself.

Optional:
Although I have referred to the member of the Holy Church with he, this was only done out of simplicity. I do not mind the main character being female.
The main character can part of either the Burial Agency, Assembly of the Eight Sacrament or Executors. His abilities and the artifacts he has are up to your jurisdiction but he should be capable of fighting against monsters. Does he practices Martial Arts? Does he own a Holy Shroud or even a Scripture? Is he capable of manifesting Black Keys by passing energy through pages of the bible? Can he use Rites combined with them? They are all allowed with the exception of the Alien Stomach World and in case of unique canon artifacts there has to be an explanation why he has them.
It is also your decision if the rumors about the Holy Relict turn out to be real and if he is going to be allowed to use them/uses them without asking his superiors.
The time and place when he meets the other demigods is not set. Or even which demigods he meets. You could even make him show up before canon.
This story should focus on the Percy Jackson-side but it is not impossible for dead apostles or others members of the moonlit world to show up. But unless they are demigods themselves, they should not be able to look past the mist.

Restrictions:
This is about the member of the Church so he has to be the protagonist. And he has to have some effects on the storyline.
I want him to genuinely belief in God and not just be a member of the Church because of his fighting powers. Thus I want his faith to have some effects and create disagreements with the demigods and gods. Refusing to sacrifice food for them, not praying to them for help and not even acknowledging his godly parent at first are a definite must. Though I don’t want him to be a fanatic that goes on a killing spree to kill all the half-bloods in the name of God.
His godly parent must not be one of the big three or any of the gods that cannot get children in canon Percy Jackson.
His human parent must not be part of the moonlit world. This is because, if the gods were trying to hide their existence from Alaya it doesn’t make sense for them to have children with someone knowing about the Counter Force.

Remember:
In the Percy Jackson-verse Gaia is a “physical” entity. This makes her one of the few capable of interacting with both sides though thanks to the mist she can only do so through the Counter Force in the moonlit world.
Alaya is an aspect of Gaia that split up when humanity grew stronger that does not like any threats to humanity and here the gods belonged to those. This resulted also in the creation of the mist since otherwise Alaya would have probably sent in her Counter Guardians, resulting in a lot of death and destruction. Over the past years Alaya just grew in power, making it similar in strength to Gaia itself, which just makes them even more wary of anyone from the moonlit world.
Since the main character is one of the few capable of seeing through the mist the possibility of him becoming an agent of the Counter Force is less then slim.
The Phantasmal Species of the nasuverse are depicted a bit stronger than the monsters of the Percy-Jackson verse. This has to do with the fact that in the nasuverse the older a Phantasmal Species becomes, the stronger it gets. So, you have to have an explanation for that. On possible reason could be that the mist cutting them off from one side of the world put them into some kind of stasis.

Shingeki no Kyoujin

Attack on Gaia (X Fate series)

Summary:
The Titans, the Beasts of Gaia, roam the lands, bringing mankind near extinction. When Alaya saw her chance, she took it and equipped seven fighters for humanity’s freedom with seven weapons of mass destruction: Servants.

Details:
Humanity has gone too far. To prevent her destruction Gaia sends out a new race of Beasts, the Titans to deal with humanity. While Alaya is busy dealing with all the Aristoteles that came to help Gaia, mankind is brought near its extinction. Nearly all achievements of science gone and the remains of humanity hiding behind three gigantic walls. One dead apostle, having learned to live of the blood of Titans, decided he doesn’t need humans anymore and out of spite for the dead apostle ancestor, decides to fasten mankind’s annihilation. However, when he creates a ritual to summon the God of Destruction just as the Colossal Titan opens the way to Trost, Alaya sees her chance. Not only is the dead apostle left with the weakest of all Servants: Avenger, but seven recruits in the fight against Titans suddenly find themselves with seven Heroic Spirits as Servants, their only purpose to help them fight against the Titans.

Optional:
Although I am not making any Servant mandatory, I would really like for seven certain Servants to make an appearance:
Archer: EMIYA (Kanshou and Bakuya Overedge- Flügel der Freiheit)
Lancer: Diarmuid of the Love Spot (Twin Roses - Protector; also: Curse of Mortality)
Caster: Hans Christian Andersen (full Marchen meines Lebens Master from the Survey Corps = Titan Shifter)
Assassin: Hassan-I-Sabbah (Cyber Fantasy big brain = big explosion)
Berserker: Lancelot of the Lake (Knight of Honor 3D-Maneveur-Gear = Awesome!)
Saber and Rider would be two non-canon Servants and so telling now would be spoilers. If you are interested in knowing them, PM me, since in my opinion they really fit for the job.
There can be some magi but modern magecraft shouldn’t be very effective against Titans.
Also Servant Summonings are a really good way to keep someone alive who in canon died.

Restrictions:
Except for the Servants and dead apostle ancestors, there should be no canon characters from the nasuverse making an appearance.
No Titan Shifter on the side of the Titans is allowed to get a Servant.

Remember:
If the Masters of a Servant is no magus, he should have trouble supplying enough prana, weakening the Servant in the process unless trained. On the other hand someone like a Titan Shifter should have no trouble supplying even Berserker if he moderates the time he lets his Servant fight.
Besides the Heroic Spirits, there are also going to be some humans influenced by the Counter Force. In fact, the description of the Rogue Titan as humanity’s wrath was one of the things that gave me the idea for this crossover.
If the Rogue Titan summons a Heroic Spirit he would probably achieve his Titan Form a bit later than canon since he has no need for that.
Since this plays after our current era, even if most technology got destroyed, the humans still have the scientific knowledge. So everything that can be created with natural materials or easily created artificial materials is fair game. It is also possible to make a less-efficient copy of a modern gadget that functions on charcoal or wood. Though all scientific advancements should be restricted to things that help killing Titans. And they should be rarer than what they had in canon since their resources are more limited.

Soul Eater

Multiply Resonance

Summary:
What would happen, if a demon weapon has dissociative identity disorder?

Details:
This story idea is about a demon weapon at Shibusen who differs from the others by not having just one weapon form but multiple ones by means of his dissociative identity disorder. The Problem: He can only transform into the weapon who corresponds with his current active personality and he cannot control the switching between his personalities. Furthermore, every personality has its own wave length, making wielding him rather difficult.

Optional:
Right on the spot I can think of two possible stories that can spring from this scenario. First, a NOT-Type story, where you focus on the interactions between the characters and how the demon weapon tries to live a rather “normal” student life or second, a story, where the character actively tries to get the fitting meister to become a Death Scythe.

Restrictions:
Do not make the demon weapon or his meister a canon character, unless it is Tsugumi Harudori. In this case you still have to remember, Meme and Anya are drawn towards her original personality.

Remember:
The demon weapon has to start as a NOT, since personality changes should be nearly as difficult to handle as Excalibur (but only nearly). However, when he gets the right partner, he could jump up to EAT and eventual Death Scythe.

Sword Art Online

Cursed Skills

Summary:
Kayaba Akihiko really liked the Unique Skills. But after some thinking he realized, only giving them to the best players would not really be fair and if they died, they would take the skill with them. But they were still too powerful to give out with just normal missions so he decided to add a little twist: The missions could only be redone, after the previous owner of the skill died.

Details:
The idea for this one came from a SAO-manga where they accused Kayaba of being a bully because he gave himself the best skill and from me reading fanfictions where the author decides to give the main character an Unique Skill right of the bat (though they’ve gotten rarer). So, I wondered if there was actually a way for Unique Skills to be distributed fairly and earlier than canon (because most fanfiction don’t even reach that far) and here we are:

Unique Skills are now not giving by the game master to promising players but are actually available through missions early in the game. Once someone cleared it and got the mission, the mission stays locked until the user died. This way they still are Unique Skills but everybody can get them.

Optional:
Kayaba planned for ten Unique Skills with six of them known in canon. How many of them you put into your fanfiction and how many other you decide on, is up to you but you should have at last 6 and max 15 Unique Skills. (If you want to know the canon Unique Skills but don’t know where to look for them, PM me and I’ll tell you them.)

Restrictions:
Every Unique Skill has to be different from the other. None should just be a more powerful version of another Unique Skill. But an Unique Skill can be a more powerful version of an Extra Skill.

Remember:
Getting a Skill, no matter which one, does not automatically gives one perfect control of the Skill. Having an Unique Skill is also not an Instant-Win-Card.
Since Unique Skills are now given to everybody, but not more than one at a time, people with Unique Skills are in more danger of getting killed or having an assassin sent after them. This also means that any person owning an Unique Skill can be accused of having something to do with the death of the previous user.
In canon Kirito and Heathcliff both gained their Unique Skills from the game master. Since this is not the case here, they might not get them.

The True Aincrad Liberation Force

Summary:
When Sword Art Online became a death game no one on the outside was able to log them out. So someone had a different idea: How about sending people inside SAO to help them clear the game?

Details:
Using the NerveGears of the ones who died even before the tutorial, they were able to sent a small task force into SAO. Kayaba, seeing as they actually follow the rules, decided to let them be since their late login into a level-based MMO gives them a handicap and their appearance encourages other people to try and clear the game.
I doubt I have to say this, but this story is going to be heavy with OC, from the task force to the other players.
Out of the people who are assigned, there should be at last one of each of the following:
A gamer, someone who has played a lot of computer games and especially MMO,
a beta player and/or a member of the staff with in-game information (though not too much since Kayaba is said to have done most himself),
a martial artist, someone who is already proficient in at last one weapon in the game, preferable a weapon-type which sword skill can be gained from the beginning,
someone who has experience with fights to the death in real life like a soldier or a police officer and
someone with experience in leading a team (this one can be combined with the previous one).

Optional:
You can include a psychiatrist and/or a priest in the group because there should be some players needing them.
If you have trouble creating suitable OC or like this option a lot more, you can also take characters from other franchises provided that those come from a real-life setting that could take place in Sword Art Online (this time I am talking about the anime). These characters can come from anime but also from other shows or movies and the timeline for those stories can be altered to fit into SAO.

Restrictions:
Getting the idea approved and finding suitable people will take some time. I doubt they would make it in time for the second boss fight but I am pretty sure not for the first. On the other hand, they shouldn’t be getting in too late so that they would still be able to catch up with the frontliners.
Do not give any member of the task force a Unique Skill unless they have reached Floor 90 and then they have to have shown the requirements for that skill. But I do encourage giving at last one of them a new weapon-type.
None of the characters in the task force should only be there as cannon fodder. Also keep the number of people reasonable, since I don’t think Kayaba would allow too many from the outside in.

Remember:
All member of the task force have to be of age because no matter how good someone is, they could die and they would not risk sending someone under age. That is why they also have to leave a will before they are accepted.
Not only the levels of the group are lower, in Aincrad the rate for dropping items and monster spawning decreases the more people are after them, adding to the other difficulties. So it should take at last some time before they are ready to become frontliners.

Yumekui Merry

Irregular Demon and Demon Hunter (X Fate series)

Summary:
In a certain city a lot of people are suddenly loosing all their dreams and ambitions, becoming hollow in the process. Suspecting the work of a demon the Holy Church sends Caren Hortensia to gather information. Not only does she find an incarnated demon that for some reason has no Reality Marble, but also a boy with Mystic Eyes that allow him to see demonic possessions. If that wasn’t enough, the number of demons appearing is high enough that it could be called an invasion.

Details:
The idea for this story came when I tried to explain the abilities of the dream demons from Yumekui Merry with the mechanics of the nasuverse and I noticed just how similar they were to the imaginary demons. They possess humans, have ties to dreams or in other words wishes and even have a Reality Marble-like garden. That just fits so well, I got the idea for a crossover. And who better to choose than the demon detector Caren Hortensia? So, here the aforementioned exorcist comes to the city that Yumeji and his friends call home – for some reason I can’t find a name – to investigate the demons and in the line of her work meets the crew and after some time (and maybe some misunderstandings) helps them out in their quest to defeat Pharos and unravel all the mysteries regarding demons.

Optional:
The person dispatched to deal with the problem does not necessarily has to be Caren Hortensia but considering she can detect demons I thought it was fitting. But if you want, you can instead chose a different character who has a valid reason to investigate like Emiya Shirou, Ciel or even an OC.
The investigator does have to meet with Merry Nightmare and Yumeji but I don’t specify when or who else from the cast of Yumekui Merry they met before that.

Restrictions:
The investigator from the nasuverse must not kill any of the main cast, be it on purpose or because of a misunderstanding. I am not saying they are not allowed to fight each other, especially at their first meeting but I don’t want it to end in casualties.

Remember:
While gardens are close to Reality Marble’s, with the exception of someone connected to dream demons, usually normal people can’t enter them. You can either keep this or change it so that it only keeps out those that have no magic circuits that they can be broken into by people with magic circuits or make them full Reality Marbles.
Caren experiences demonic possessions with her own body.
If you want Shirou to meet with the cast you have to remember that Yumeji is a faker of a different sort and Merry may or may not have a move that allows her to destroy Reality Marbles.

Mystic Eyes of Dream Perception (X Tsukihime)

Summary:
Since he was young Yumeji could see things that other people couldn’t. When he looked at a person he would see spots in multiple colors on them, even though there was supposedly nothing wrong with his eyes. He didn’t knew what they meant until one day he met a man possessed by a demon and his eyes showed him a pattern he had never seen before. The Exorcist dispatched to deal with the demon noticed his special ability and took him under his wing to train him. When years later he heard of incidents in his home town that were speculated to have to do with demons, he was the first to volunteer. But once there, he met an irregular demon that soon turned his whole world upside-down.

Details:
The dream demons of Yumekui Merry are a sub-species of the imaginary demons of the nasuverse. And Yumeji has Mystic Eyes that lets him see if any human is possessed by an imaginary demon. An Exorcist notices this and asks him, if he want to learn how to fight and exorcise demons. Yumeji accepts and becomes a part of the Holy Church. After some years of training and maybe some missions Yumeji makes a name for himself. And after he hears of suspicious activities in his hometown, he volunteers to investigate. There he meets Merry Nightmare, a fully incarnated demon without a Reality Marble with no memories of how she got there and or how to return. Together with her he fights against what amounts to an army of demons, all the while trying to unravel the mysteries that surround his new companion and find a way to send her back home.

Optional:
It is up to you, how or when Yumeji awakens his Mystic Eyes but he should return home at the time that Merry is there, so he shouldn’t start his training too late.
I personally would like to see his training and his first missions, too, but if you want you can just jump to the time when he gets back to his hometown.
It is also up to you if Yumeji becomes only an Exorcist or if he further receives training as an Executor, too and how well he does in the latter.
In canon Yumeji’s eyes have a rather specific restriction for its usage. Since they are Mystic Eyes here, it wouldn’t be so surprising for him if he could activate them at will or if they were even active all the time. If you decide on the latter, he might need a pair of Mystic Eye Killers.

Restrictions:
Other people from the nasuverse shouldn’t make a lot of appearances. The focus should be the cast of Yumekui Merry.

Remember:
Yumeji’s eyes mainly allow him to see dreams and finding demons is just the most useful application they have.
Since he also gets taught the philosophy of the Church, he should see all imaginary demons as disturbances at first but meeting Merry and other good dream demons should change that.
Since Yumeji is gone for a long time and taking over a host is a long process, not to mention that Yumeji is now an Exorcist, the meeting between him and John Doe should definitively play out differently than canon. It wouldn’t be farfetched for John Doe to choose a completely different host.