Thirty years after the Demon King who ruled the world was destroyed. A nurse working in a clinic with one of the Knights of Light, Yamazato, who has retired from active duty. The news of the resurrection of the Demon King arrives... and by a strange turn of events, Yoshine Kyoko becomes the hero.

Marie Iitoyo failed to confess to the man she loved. As she's at home regretting her decision, a little man appears in her room and hands her something called a "reset button". Marie pressed the button fearfully, but...