Satsuki

The older twin sister. Small-breasted. Clumsy but hardworking. She tries hard to show her younger sister Mai her serious older sister persona, but in reality, she's a clingy, lonely person.

Lonely from living apart from her parents and sister, she started a physical relationship with her uncle and found pleasure in it. Plagued by guilt, she begged Mai to keep it a secret and accept it.

Devoted to her sister, she suppressed her own feelings and returned home with Mai when her sister expressed a desire to come back together.

The secret relationship eases the loneliness of living apart from her parents. She secretly worries about having smaller breasts than her sister.