A shut-in gamer discovers the one person on earth who remembers him as something dangerous. She's still furious about it. The show finds comedy in the fact that they're the only two people in the world who know what they actually are to each other, which means every grocery store trip and cafeteria lunch becomes a negotiation between someone trying to disappear and someone who came back specifically to finish what they started.
Ryuusei Narukami carries a secret that would shatter his carefully constructed new life: he's the reincarnated Demon King, now living as a reclusive shut-in. His second chance at existence was supposed to be quiet. That plan falls apart the moment Meteor Hanaori transfers into his classroom. She's the legendary Hero who defeated him in their past life, except now she's a normal high school student with no memory of who either of them really are. Forced to maintain his cover as a teacher while she sits in his class completely oblivious, Ryuusei finds himself spiraling. The girl who once wielded a sword against him now wants to fight about everything: class rules, his grading system, his general attitude. Every argument, every clash of wills, stirs something complicated beneath the surface. As their conflict intensifies, Ryuusei realizes the real danger isn't her discovering what he is. It's that his feelings for her might be just as powerful as his hatred once was. Watching them circle each other, caught between past enmity and present attraction, becomes its own kind of battle.