Recently, my sister is unusual.

After the Kanzaki parents remarry, their newly blended household includes a teenage son and daughter trying to adjust to unfamiliar roles. High school freshman Mitsuki Kanzaki, still carrying the scars of absent and abusive father figures, keeps her distance from both her stepfather and her stepbrother, Yuuya.

Everything shifts when an accident sends Mitsuki to the hospital and she awakens to an unsettling new reality: she’s been possessed by Hiyori Kotobuki, a girl her age who died with lingering feelings for Yuuya. Unable to move on because of that unfulfilled love, Hiyori insists on pursuing it through Mitsuki’s body—forcing Mitsuki to navigate awkward supernatural complications, uneasy family ties, and emotions she’d rather not confront.