Stunning 15 years old Yamada enters the high school with an ambitious dream: to have one hundred sex friends! The problem is: she is a virgin, and she hasn't even has a boyfriend! When she meets the shy - and also virgin - Takashi Kosuda, she chooses him as her first "victim". But as the story progress, Yamada's plan isn't looking that it is going to reach any place ever, as she begins to have feelings for Kosuda.