A family living in an apartment complex on the outskirts of Tokyo—father, older brother, and younger sister. The 21-year-old sister attends university and has long acted as a mother figure, supporting the family emotionally. Meanwhile, her 32-year-old brother is a shut-in, still living at home and spending his days in his childhood room. For the past year, the sister has been giving in to her brother's sexual desires. She harbors a secret—her entire body is an erogenous zone—and though she understands the wrongness of their relationship, she can't help but feel pleasure. This story explores the fragile family bond and the hidden desires tearing them apart.