Izaya wakes up in a coffin with nothing but a flashlight and a cell phone. He doesn't know where he is or how much air he has left. All he knows is that he's running out of time and there's only one person who can save him – Heiwajima Shizuo.

Not only is Yuuri suddenly informed that he will be the next demon king, but he hopelessly falls in love with Wolfram, who ran away from home to avoid a political marriage. Wolfram is only too glad to raise a demon king, though unknowingly. Yuuram.