As summer draws to a close, thunder rumbles in the evening sky. Aiko lies feverish with a summer cold, her consciousness hazy. In that vulnerable state, she is taken by her older brother, filled with his seed, and experiences for the first time the ecstasy of a woman. From that moment on, her body begins to change. Her innocent eyes contrast with her athletic frame shaped by club activities and her still-developing youthful form. Her now-larger breasts accentuate her impure eroticism, radiating the allure of a lewd younger sister. Slick school swimsuit toy torture, tongue-in-pussy teasing, raw sex in uniform, forced masturbation in the bath, creampie after creampie coating her pussy… This is the complete record of forbidden, perverted intercourse with a sister just entering puberty. This work is a shocking depiction of her very first sexual experience.