"The world average age for the first sexual experience... 17.3". Is that early? Late? Seno Sakura has a serious personality. Hara Tsumugi has never liked a member of the opposite sex before. Minagawa Yuna is experienced and is currently dating a company employee. At the age of 17, the girl's "sexual values" begin to fluctuate.
Sakura grows nervous when her boyfriend invites her to his house. Having no experience with sex, she turns to her friends to help her prepare.
Tsumugi gets invited to the movies by a male childhood friend she hasn’t seen since junior high. At the end of the night, she comes to a realization.
Yuna excitedly tells Sakura and Tsumugi about her new 26-year-old boyfriend, but when her stomach begins to hurt, they fear that she is pregnant.
Sakura hears odd sounds coming from her mom's room. She tells her friends about it but is shocked when Yuna suggests her mom is using a vibrator.
Feeling confused about Yu's sexual orientation, Sakura consults Tsumugi and Yuna. Later, she blames herself when rumors about him spread at school.
When Yuna fears her boyfriend is cheating on her with a larger-chested girl, she follows him and is horrified to see him entering a brothel.
Tired of her father asking her about her love life, Tsumugi decides to enter a speech contest to win a scholarship and move out as soon as possible.
Sakura worries about her friend Narumi after learning that Ryusei got her pregnant. When Narumi faces expulsion from school, Sakura makes a bold move.
Following an argument with her mom, Sakura runs away from home. The next day, she returns with Yu to speak to her mom about their relationship.
