The hidden Prince of Gehenna
Cover by @obsidianix
Story idea by @CaiyaContortiana2315
Through unfortunate events, Rin and Yukio are separated at birth, with Rin living in Gehenna with his mother and father, and Yukio living with Shiro Fujimoto.
Growing up in Gehenna, Rin is oblivious to what normal life is like in Assiah and decides to abandon his duties as demon king to see it. Through a bit of luck he manages to enter True Cross Academy under a disguise and see his twin brother for the first time.
Meanwhile, with Rin gone, his mates', Amaimon and Lucifer, decide to follow him to Assiah and promptly abandon their duties as well.
With three Kings gone, hell is in a vulnerable state and Emilia the hero chooses that moment to attack!