One of the male students, Hiroki Komachi, tries to have a word with Nayu, but ends up getting occupied at every chance he gets. Nayu, Haruka and Yako take a look at the Crafts club, but leave when the club's adviser, Tsukamoto, shows disdain to the idea of making underwear. Noticing Nayu is disheartened, Yako suggests that she make an Underwear Club herself. The next day, Hiroki complains to Nayu concerning an apparent rivalry, but is annoyed that Nayu doesn't remember him. Nayu enquires about how to start her club, but is put down again by Tsukamoto. However, after looking at the underwear her grandma gave her, she perks up and starts asking around for members, but has trouble finding any. Hiroki talks to Nayu, suggesting that she should try and put across her vision of underwear for better results.
The story revolves around Nayu Hayama, who embarrasses herself on the first day of middle school by accidentally showing her adult panties. As two other students, Yako Jingūji and Haruka Shiraishi, hear rumors of her engaging in "enjo kōsai", or compensated dating (which often is viewed as being close to or the same as prostitution), they investigate. They soon learn that Nayu is an 'underwear monitor' who tests new underwear products, and has great insight on what underwear people should wear. Nayu hopes to help everyone get through the vital stage of their life by opening an underwear club.
