Rules about fusing in this fanfic:

- When two hearts fuse, their bodies and minds become one. This creates an entirely different entity, as opposed to two minds sharing a single body. But in this fanfic, it depends how in sync the two are in order to fully complete a perfect fusion. So there are two stages:

- Sora and Roxas can be heard in their mind talking, but it still requires both to agree in order to act, voluntarily or involuntarily. Hikari is his own mind, but Sora and Roxas are more verbal in communicating at this stage. Because Hikari is technically Sora and Roxas, Hikari can't think properly if they are speaking - in their mind - as individuals, and thus, isn't entirely a perfect fusion.

- Sora and Roxas are not heard in their mind talking, but that doesn't mean they aren't communicating entirely. Because they are perfectly in sync at this point, Hikari's actions will automatically be the combined actions of both Roxas and Sora. Roxas' and Ventus' thoughts, having the same voice, are both in italic. Sora's thoughts are bold and Vanitas' are underlined. Hikari's thoughts are both italic and bold, and Maku's thoughts are bold and underlined. Maku is an unexpectedly perfect example of Stage 2, because Vanitas and Sora rarely ever speak to each other in their thoughts like spectators, only doing so once or twice.

- Within canon, imperfect/toxic relationships like that between Lapis Lazuli and Jasper in Steven Universe mean their fusion has a lot of extra limbs and does not have a new voice actor, meaning it's sorta an example of #1. They can't function in unity, so they're constantly fighting for control. Fusions, in general, tend to go more smoothly with Sora due to the helping type of person he is, even if he was in discord with Vanitas at the time. If Maku hadn't met Aiko, then he would've been much more unstable and fell apart much sooner. Aiko was the one point both Vanitas and Sora could ground the fusion in in order to last longer.

- Some dominant features in the individuals can occur in their fusions. (Ie: Roxas' rings and Sora's gloves.)

- One component person can take control of the fusion. It is also possible for different people to take control of different parts of the fusion. There are some times where Hikari will be speaking as Sora or Roxas. An example of Roxas speaking prominently is when Sora tells Riku and Kairi about Hikari. "Um... We kinda can't right now. To put it simply, we're too comfortable like this. Problem?" Another example is when Vanitas controlled Sora's feet so he'd keep crashing into walls. (Even if that technically wasn't even a fusion sssshhh).

- While all fusions require consent, a fusion of hatred is inherently unstable. Because Roxas and Sora were fighting internally about Riku asking them to unfuse, Hikari's form wavered and would have split apart if they hadn't come to an agreement. Vanitas is able to fuse with Sora even if they are at odds since Vanitas has an affinity of fusion, not being entirely whole. Sora, yes can get mad at people and hold grudges - like with Maleficent - he prefers to try and help any way he can if he doesn't see a bad outcome. (Which, again has been evidenced when Sora trusts Maleficent to hold off the heartless in Kingdom Hearts 2 even after being enemies for quite some time)

- Fusions still have all their original abilities, except with Maku who can't summon Kingdom Key. Kingdom Key chose Sora, and so while Roxas and Xion can wield it, Vanitas cannot. Since Vanitas is a bit more cocky, it's a general rule of thumb that in any fusion he takes part in, the fusion will be more darkness leaning and prefer Void Gear, because Vanitas feels he has more power than everyone else. I'd have to look through the keyblades to see what one would be a perfect fit for Maku specifically.

- Maku can't summon two keyblades because it is only one keyblade per wielder, and because he is technically his own entity, he has only one. Roxas can wield two due to his connection to Xion, so Hikari can wield two also. But because Roxas gave up searching for Xion in Chapter 2 or 3, Hikari has difficulties afterward summoning a second keyblade. If he ever remembers Xion with the memories inside Sora, Hikari will lose the ability completely.

- Memories made before and during a fusion can be held over, as Hikari recognized Riku and Kairi despite him never meeting them personally. However, people who fuse together don't automatically share their memories with each other, seeing as Vanitas manipulated it so Sora wouldn't find out who he was, as Maku was explaining Vanitas' past to Aiko.

- In order to fuse, they must be in perfect sync mentally, physically and emotionally. In Steven Universe, fusions are formed when two or more gems do a synchronized dance. And because Roxas and Sora haven't danced yet, this second fact isn't used here. Rather, Hikari relies on intimacy. To put it simply, Roxas and Sora must be touching or embracing in a close proximity. Most of the time, they hold hands or hug. Again, this isn't the same with Maku, who has Vanitas and Sora fuse together due to a mutual pain and Vanitas darkness being absorbed by Sora's heart unintentionally.

- If when they are touching and the fusion is successful - because it could fail - Roxas' heart will react to Sora's heart and they will revert to their most basic element, in their case, light. The individuals transform into an amorphous mass of energy before fully transforming and taking on Hikari. If Vanitas and Sora were to fuse normally, it would be much harder and require a lot of mutual trust, due to Vanitas' element being darkness and Sora's element being light. The two elements would naturally repel unless there is a strong bond. (But then again you could argue because of Vanitas' fusion affinity this repulsion would be somewhat nulled, but still apparent.)

- Each fusion embodies a relationship between the participants. Fusion is not inherently romantic, and other fusions can embody other sorts of relationships such as the social relationships between friends, allies or even enemies. The more perfect the relationship, the more "normal" the fusion looks. Maku has an extra set of eyes and arms, while Hikari has the correct amount of limbs and body parts.

- The appearances of the participants blend together as a fusion, such as Hikari having a mix of brown and blonde hair, he also has a different face. Because Vanitas originally didn't have a face, Maku doesn't necessarily just look like "Sora but with black hair". He looks like an altered Sora to some extent, looking more mature. In fact, as kind of a joke, his appearance is mainly white, having white hair, very pale skin and white outfit. He has his own version of Vanitas' mask, which is a upper white animal face mask, similar to the ones from unchained x, but he never wears it in the story. The white is due to all the light he creates, even if he is over ¾ darkness. The light is due to Sora's heart consuming Vanitas' darkness and converting it into something he can somewhat use. Because too much light would hamper Vanitas', the light spills out into his appearance, affecting the way Maku looks.

- Usually a fusion is the combined height of the individuals, but because I don't want 10ft characters walking around, I didn't really keep this. Maku is taller than Vanitas/Sora, by a tiny little bit, while Hikari is taller knocking in around Riku's height. (Depending on who you ask between the two, they'll probably say they're taller than the other. But alas, the world will never know.)

- Fusions tend to highly exaggerate whatever personality traits are shared amongst the majority of the hearts comprising the Fusion. Sora and Roxas don't like being undermined or manipulated, so Hikari is very quick to jump to analysis of things that may have a negative meaning. Because Sora and Vanitas are two very contrasting personalities, Maku most of the time resorts to indifference, not wanting to get involved unless he has something to prove or protect. If the situation doesn't hurt his pride in someway, he won't even care. His main trait is pride, and will easily step over the line to get his point across. He is less calm and collected in these moments, acting more on fueled emotion in battle when he defending his pride. He can get cocky, especially if he wants to show off. (Which is a trait Sora and Vanitas both have, believe it or not.)

- Fusions have their own unique weapon. Hikari does have his own keyblade, but defaults to Kingdom Key seeing as it is Roxas and Sora's own default, at least before Roxas changed his preference to Oblivion and Oathkeeper. Two Become One is one of his favourites, seeing as it represents Roxas, and allows Sora to unlock Final Form faster, a form which uses Roxas' abilities. It just represents Roxas coming to terms with Sora, so ye. Maku doesn't really have a preference, choosing Void Gear mostly because he fights with Vanitas' style.

- What Roxas and Sora do at the end of the series is called a perma-fusion, where two hearts stay bonded together outside a short period of time. A fusion can change how he or she wants in appearance if they are in the same mind. In Steven Universe, even perma-fusions can separate, even if it's few and far between, but due to the nature of the story, Roxas and Sora are pretty stuck. It'd cause some serious chaos between the two to create darkness and separate them.

- The last line of this story is actually an answer to the last line in the first chapter. The first chapter ends with "I love you.". The last chapter, ends in the same way, but this time, it's an affirmation of their love. That, even after all this time, all they have been through, Sora still loves Roxas, even if he has experienced doubts over it. In the beginning, the way that Sora and Roxas view Hikari, is very different. Roxas wants to express his feelings for Sora through Hikari out in the open, with no fear or shame, while Sora sees it as more of a private thing, something he doesn't quite understand, but is open to experiencing. By the end, Hikari is sure of himself, opening his eyes in the real world and embracing their shared truth.

- The last chapter is supposed to mimic the first one loosely, starting with Kairi's POV and ending with the confession.

Few Audience Members: "WHAT'S UP WITH THE LACK OF FUSIONS? I NEED MORE FUSIONS IN MA LIFE!" Today I shall reveal to you all the fusions I've thought of:

- Vanitas and Roxas aka "Osiria": Osiria is the name of a rose that is a blend of both red and white. Vanitas has always reminded me of a rose; his veiny suit like roots upon the ground, the appearance of Sora but with thorns along the spine. Osiria's hair kind of looks like the rose: his hair with a base coat of white with lines of red twirling into the stem and each spike of hair tinted red. He wears a Hakama, but it's more like armour, since all pieces of his clothing is shaped like petals. I wanted to make him look like he was ready for combat at any time, because he's the most aggressive/fight-me fusion. He'll take anything you say the wrong way and will smile as he beats your head in. In order to have a creepy edge, he looks a bit like a spider: having 6 arms and 4 eyes (two huge and two small off to the side). He has the biggest attack power out of all the fusions, is one of the fastest, but has like, no health. He's a glass canon, so if you can get him down - good luck - he'll stay down.

- Sora and Ventus aka "Raven": The name is something I'm pretty proud of; So[Ra] [Ven]tus. That's it. Just a mash up of their names that isn't obvious and looks like a legitimate name someone would place upon their child. Speaking of, Raven isn't the youngest fusion - that goes to Toxin - but he's definitely 14. He's similar to Hikari, except his hair is much more lighter/brighter, and he's shorter. His clothing is pretty similar to Hikari as well, but it definitely has a blue accent to it due to the whole sky theme: Raven is a bird, afterall. He's the most gullible, kind, and trusting person you'll ever meet. It takes a lot to set him off if it's not directly pointed out to him. Then he'll get angry at himself "How could I be such an idiot!" for not seeing it sooner. He'll rush to help however he can and put a lot of effort into it. He's got a moderate strength, just under Hikari, but he's got a lot of health and defence (the most out of the fusions), focussing more on the speed aspect.

- Xion and Vanitas aka "Toxin": this name is Xion's name anagramed with Vanitas' T thrown in for good measure. Instead of using "they" like any other fusion of two different genders, Toxin is genderfluid. These two characters technically have no gender? I mean, obviously Xion is a girl because of Kairi, and Vanitas is based from Ventus/a boy, but they are both artificial beings. Idk for Vanitas I'm stretching it, but Toxin is genderfluid, so they don't care if they're referred to as either he or she, and as such, I'll be jumbling them around. Xion, canonically, doesn't even live to her first birthday, and Vanitas is canonically four (in terms of from birth to death) so Toxin is five years old. He's got androgynus short black hair and really dark murky purple-blue eyes. It's really hard to describe her outfit, but I definitely thought about that Aladdin inspired sultan outfit for my girl character in Unchanied X, but with a purple and black colour scheme and a decaying butterfly as inspiration. He has feathers scattered throughout the outfit, and a fabric covering the bottom of her face to hide the fact they have two mouths. He has a single black glove. Toxin excels in magic and cannot physically wield any weapons, because they don't make keyblades for five year-olds lol. She is someone who can make a lot of dash-hit-evade type attacks, running in and running out. His personality is very undecided because I literally only thought of making Xion fusions after Ima's review XD. Ummm, he is someone who doesn't talk a lot, isn't expressive unless the matter calls for that seriousness or urgency. When Toxin talks there's this female voice that's clear and precise and a rumbling raspy voice that's undefined in gender talking underneath it. It's kinda slow, cryptic, and like a snake's. He's very to the point, do what needs to be done, regardless of the situation or others in her way. In that way, she's kinda like a child, often becoming frustrated if he doesn't get what she wants.

- Roxas and Ventus aka Nope.

- Roxas and Xion aka "Orion": Apparently it means "Rising in the sky; dawning" and I gotta keep with the sky theme am I right? Basically a female Roxas in appearance, dark grey hair. Don't know much about this one. They use "they", have earings. Again, I never really considered Xion before.

I'll definitely be making a Roxas/Sora/Vanitas fusion chapter at one point, but if you have any other questions about fusion or this story in general, feel free to ask! Would you guys like to see my thought process behind this story lol?