During a class trip to a remote island, Muneto and Kayo are targeted by a legendary Demon Beast that believes Kayo is its mother. As the creature captures students to fuel its rebirth, the pair must navigate the island's tragic folklore and locate a lost Maitreya statue to stop the monster. Despite the interference of a delusional follower, Kayo and Muneto manage to invoke the statue's divine power to defeat the beast and save their classmates.