Plot:

Right after Yuri Egin gives birth to both Rin and Yukio, Fujimoto and Mephisto aren't the first ones to show up. Instead, a gate to Gehenna is opened in the cave and a demon takes the only twin that is known to have demon blood -Rin. Fujimoto and Mephisto show up after Rin is taken away (with Yuri's blessing.)

Rin grows up as a respected Prince, Heir to Gehenna because of his blue flames. Yukio is raised as an only child under Fujimoto's care and enrols into the True Cross Academy to follow in his father's footsteps, at the normal pace for people his age.

Rin has always been curious about Gehenna's mirror wold; Assiah. And sure, he's visited the dimension quite a few times, but he doesn't get to fully experience it for a long period of time until one day he's suddenly summoned. And if some exorcist being powerful enough to summon and control him isn't enough, well, he's even more shocked when he finds out that it's his human twin that does so. Or maybe it shouldn't be such a surprise...In any case, he's always wanted the chance to get to know his mysterious brother.

Rin has always known of his parents' dream to one day emerge Gehenna and Assiah together, but the more time he spends in Assiah and with humans, the more unsure he is of that plan. He grows to love Assiah and some of its inhabitants -he'd hate to see it all be ruined with the harshness of Gehenna. However, his father is very determined and prepared to go to war for it...

Rules:

1) Rin and Satan must have a good father/son relationship. No abuse -of any kind. You may have corporal punishment, and strict/heavy/harsh training, but no matter what it can not cross the line of abuse. Furthermore, show some of Rin's childhood.

1.5) Rin loves his life in Gehenna. Gehenna and the castle that he lives in is his home, and the Demon Kings and Satan his beloved family. (Although like all families and homes, they aren't perfect.)

2) Because of Rin's new environment, his character is going to be different. At his core, Rin is an honest, loyal, and compassionate man -although admittedly a stubborn and hot-headed one. With his different upbringing, Rin will not be childish or sensitive as he is canonically, more brutal/blood thirsty for those that wrong him or his, and will be very confident in his many abilities (perhaps viewed as arrogance by others.) He will still be extremely loyal to his family/friends and compassionate in his beliefs. Rin, having been personally trained by Satan and the best trainers that Gehenna has to offer, is largely more powerful and deadly than in canon. He is also a lot more manipulative, sarcastic, and book smart than in canon. Yet out of the two types of smarts, he still leans more towards the street kind. (Textbooks and a stuffy classrooms just aren't his thing. Cooking and being physically active is so much more fun.)

3) Obviously, Rin won't have to depend on his sword or another object to control his flames and demon appearances. You can still make him use a sword to fight, however, if you want.

4) Satan loved Yuri, and Rin and Yukio are half of Yuri. Satan would have taken Yukio as a babe, also, if Yukio hadn't been so human. Gehenna is not meant for such fragile creatures that humans are. Rin knows and understands this.

5) Yukio summons Rin on his first attempt/trail to see if he has any skill as a tamer. He is no younger than fifteen at the time, and has no idea (at first) that the powerful and humanoid demon that he summons is his twin. But Rin does.

6) Have some world building. What's Gehenna like? The environment, geography, the social structure, and demon culture? Also, as shown in canon, demons have their own language. So while Rin can definitely be fluent in Japanese, it's not his first language.

7) The decision if Rin chooses to follow Satan's grand plan to emerge Gehenna and Assiah together or not, and whom he fights for and against, is entirely yours.

8) No romance or romantic feelings for characters that are under the age of fourteen! Furthermore, there will be absolutely no incest or pedophilliatic action or themes!

Suggestions:

* Have Satan speak in Yuri's mind before Rin is taken away, to explain and talk things through -although admittedly it will be a short conversation since Yuri is dying.

* Have Rin have demon friends that aren't his family. No one wants to hang around their family all the time.

* Have Fujimoto retire as an active exorcist and teach at the True Cross Academy.

* Have Satan find a way to make Rin immortal like the rest of his kids. Because despite how powerful Rin may be, he still is only half Demon and utterly mortal life-span wise.

* Have Rin view humans as the weaker species, not necessarily because he's bigoted but because they are factually, physically weaker and die from wounds that demons and himself wouldn't.

* Have Yukio trust no demon and perhaps even hate them. This will create conflict and make it more sweeter if/when Rin and Yukio grow close as brothers.

* Have Rin be able to create his own Gehenna gate.

* Have Rin be able to summon another demon himself. He is half human, after all.

* Have Yukio unlock his blue flames (by accident) after a life-threatening situation. Of course, Rin can't be happer when this happens. Because now he can show Yukio Gehenna, Yukio can fight better, and he can learn how to control the flames with "Father's" (Satan's) teaching like Rin had when he was a kid. Yukio however...

* Other story titles, aside from Across Dimensions, are: Separated At Birth, Summoned, My Human Brother Summoned Me, Long Lost Family, A Whole New World, Blood Of My Blood, My Evil Twin, and One Hell Of A Time.

Please review or message me if you're interested in taking up this challenge.