Chizo Kamiya, a seemingly ordinary office worker, has a secret. It is that she can see "a certain number" above a person's head. That number is the number of days since the person last had sexual intercourse, or in other words, "purity fighting power!"
Because of this ability, Senzou, who once broke up with her boyfriend after learning that he was cheating on her, has been interested in Miyoshi Kiriri, a high-spec boy in her class, but has been unable to take the first step forward. There was one more thing that was bothering Senzou. That is, the number above Miyoshi's head is over 10,000, which means that he is a virgin. "Why is it that he is handsome, good at his job, and has a good personality?　Why has he never had a girlfriend?"　I wondered, and then, at a drinking party, we started talking about his past relationships.