Yamada is starting high school for the first time. She's got a great body, great looks, and she has a problem with something "down there". Being unsatisfied with remaining a virgin, Yamada has set the goal of acquiring 100 different sex partners over her high school career. However, her imagination takes things too far, and she keeps screwing it up.
After scaring off one-too-many boys with her attitude, she tries to fall in love with a "normal" boy she met at a bookstore. However, she makes fun of his own virginity by accident before even learning his name (Kosuda), steals his textbook, tries to "reverse rape" him only to chicken out at the last second, and takes things too far when they're both alone in the library stacks, causing the boy to wonder just what the heck she really wants.
Yamada tries hatching a plan to steal Kosuda's umbrella on a rainy day so they can both walk to his house together under her own umbrella, and it seems to work when she gets into the house and alone with him after his big sister leaves. However, after seeing him get a boner, Yamada gets scared, shoves him off and runs back to her own house. Even the manifestation of her "H-side" sighs and claims that Yamada's goal is going to require a lot of work.