After being laid off, Yuki ends up staying with his older brother Takashi while he looks for a job. At home, he meets his beautiful sister-in-law, Waka, who is a complete mismatch for his arrogant brother, and Yuki wonders why she married Takashi. Waka is pure and has never dated any other man than Takashi, so there is no way her sex life with the arrogant Takashi will go well, and she loses confidence. It's a waste to let her have such a beautiful body and such charm. Thinking this, Yuki decides to teach Waka the joys of sex in his brother's place...