Kozue Kirishima is an airhead. She is the only student that attends supplementary lessons, all alone with her beloved teacher Mori, and today she hopes to finally confess her feelings to him. However, her plans are ruined when another teacher, Komori, announces that due to some urgent business, Mori had to leave and he will be teaching in his stead.
As the class begins, Kozue starts asking questions about Mori, regarding his younger days, personality, and preference in women, to which Komori apparently knows the answer: virgins. Taking advantage of her naïve personality, Komori offers to check if Kozue meets the requirement!