The Kurahara family consists of two sisters and a younger brother. Responsible Miki is married and lives away from home, gentle Mao works an office job while living with their parents, and youngest sibling Ko is an adult university student living alone in Tokyo. When the family reunites, Ko returns tattooed and rebellious after a woman his age rejected him for being too thin and weak. Though initially angry and confused, Miki and Mao decide to bare themselves and rebuild their beloved adult brother's confidence through soothing encouragement, forbidden threesome sex, and creampies.