Yamada Seina's life is already teetering on the edge—between juggling high school, managing her friendships, and covering her rent solo, she barely has time to breathe. But when she nearly falls prey to a scammer and loses her hard-earned rent money, things go from bad to worse. Just when it seems like she's hit rock bottom, a mysterious (and incredibly handsome) stranger with horns swoops in, claiming he’s a demon king who's crossed dimensions just to be with her. Why? Because, according to him, Seina is the reincarnation of his lost love! Skeptical but unable to shake him off, Seina finds herself with a new, otherworldly roommate who's hellbent on keeping her safe, whether she wants his protection or not. What's a girl to do when her biggest problem suddenly becomes a supernatural—and superhot—roommate?