Saikin, Imouto no Yousu ga Chotto Okashiinda ga.
最近、妹のようすがちょっとおかしいんだが。
A high school girl named Kanzaki Mitsuki has a new older brother after her mother remarries a divorced man with a son. When her mother moves abroad with her new husband, Mitsuki is left alone with her stepbrother, Yuuya, and keeps her distance from him. One day, a spirit named Hiyori enters Mitsuki’s body and attempts to seduce Yuuya. Hiyori is a girl’s spirit who died and cannot reach heaven. To advance toward the gates of heaven, Hiyori uses a device on Mitsuki that fills up whenever Mitsuki experiences sexual feelings toward Yuuya, such as from dates, kisses, or intimacy. Each time the device fills, Hiyori moves closer to heaven. To remove Hiyori, Mitsuki must take provocative actions toward her stepbrother.
