Pin-chan, a high school girl, puts a Valentine's Day chocolate in Kin-chan's shoe box, even though he has been strangely distant lately. The next day, the school is closed due to the spread of a new type of virus. In order to retrieve the Valentine's Day chocolate, Pin-chan tries to break into the school, but for some reason, she ends up going in with Kin-chan, who says he forgot something important inside… (Source: Natalie, translated)