After eradicating the ghosts from a haunted schoolhouse years ago, a former student discovers their unwelcome return and quest for vengeance. Following their mother's death, Satsuki and Keiichirou Miyanoshita relocate to her hometown to cope, but their new academic institution is the notorious haunted edifice. Despite their initial skepticism, the siblings soon recognize the spirits' presence and curiosity towards them. With the aid of their feline companion and newfound allies, Gakkou no Kaidan chronicles these siblings' hair-raising encounters as they attempt to outsmart the school's ghosts.