Okano Yuki, the ace of the baseball team, is dating Uesugi Satoru, the club's manager. One day, while walking home from school, Satoru musters up the courage to invite Yuki to his house but by chance, they bump into Satoru's younger brother, Tatsuo. Tatsuo, the complete opposite of Satoru's gentle appearance, consistently belittles his older brother. Seeing this, the strong-willed Yuki can't keep quiet and expresses her anger towards Tatsuo. Later, when Yuki reunites with Tatsuo, she is taken aback by his seemingly different appearance, not only lacking his previous condescending attitude but also revealing that he "wants to apologize for what happened last time." So, despite being invited to Tatsuo's house (which is also Satoru's), Yuki is fooled by his sudden change, falling right into his trap and having his weakness exposed. Despite it being Yuki's first sexual encounter and being the worst possible partner, Tatsuo's technique and huge cock bring her to a spectacular climax and without Satoru's (older brother) knowledge, Tatsuo (younger brother) takes her virginity. Even during sex, Tatsuo mocks Satoru. Yuki doesn't approve of this and Tatsuo, impressed by her strong personality, urges her to "become my woman" but she firmly refuses! This assertive attitude only fuels Tatsuo's passion...