My older sister is simple and introverted, but once she takes off her glasses, she's an absolute beauty. I couldn't resist pressuring her, and she let me have my first time inside her with an unprotected penis. (Yuki Kosai ROYD-271)

The taciturn and unassuming stepsister, Aya, always appears expressionless at home, wearing glasses and no makeup. One morning, however, she appears with a little makeup on. Her caring younger brother, in response, gradually undergoes subtle changes. Finally, he can't hold back any longer and confesses his long-held feelings. Although his sister rejects him because of their sibling relationship, they agree to finish only with their penises, rubbing their groins together. Although it ends at one point, they can't forget the excitement and finally penetrate each other. Once they have sex, they can't stop, their bodies and minds constantly intertwined.