Yamada tries to get busy with Takashi Kosuda at the pool while Miharu Takeshita brings her boyfriend Daisuke along. Yamada ends up going on a water slide because Takashi grabs on tightly to her body, but in reality he's just scared of heights and going down the slide.
Later that night at an oban festival, Takashi decides to take the initiative (with Daisuke's urging) and hugs Yamada for real. Yamada is inspired enough that she goes out and buys several boxes of male condoms in preparation for...something.
The next day, Yamada is trying to think of how to present a bunch of condoms when she sees Takashi being friendly with another girl who has glasses and F-cup breasts. Takashi's sister Kazuki mentions that girl, Mayu, has been a childhood friend since both their families have been living across the street from each other for several years and have been on good terms with each other. However, Yamada is scared because she's afraid she'll lose Takashi to Mayu, so she sees her as an enemy and plans to humiliate her at school the next day. Instead, she ends up accidentally encouraging her to become closer to Takashi.