The story is set in a near-future Japan - an era where people can freely alter their appearances, resulting in a society teeming with individuals who share the same face. A university student living with her "natural face" finds herself consumed by a growing sense of unease and anxiety after discovering a mysterious "X" mark drawn on her mirror. Eventually, she walks through the doors of the renowned "Rei Face Clinic" and confronts the choice of whether to change her own face...