Mitsuki (played by Tenka Hashimoto) and Yuya (portrayed by Yukichi Kobayashi) find themselves as stepsiblings following the marriage of their parents. Mitsuki struggles to connect with her new family, while Yuya is unsure of how to interact with his stepsister. The situation takes a supernatural turn when Mitsuki is possessed by the spirit of Hiyori (Mayu), who harbors feelings for Yuya and believes he can assist her in reaching the afterlife. To achieve this, Hiyori fastens a leather chastity belt on Mitsuki, setting a plan in motion to guide her spirit to heaven.