Shiro, staying at a friend's house, unwittingly stares at his sister Nao's bra-less figure. The bra he accidentally picks up in the changing room is shockingly an I-cup. While sleeping next to her brother, feeling the guilt of not wearing a bra, Nao trembles in shame as he points it out and forcefully hugs her. A story of pure love and endless fucking with a busty beautiful girl, overflowing with first love's passion.
