After Kiyono joins the society, the girls become aware of her habit of teasing what's under her skirt in front of boys. She flips up Yako's skirt and makes fun of the underwear, only to show some embarrassment when she flips hers back. The girls are surprised when Kiyono takes off her underwear before leaving. The next day, a moral exam is held and Kiyono is told off for wearing makeup. In the meeting later that day, Nayu brings a deconstructed bra, but Kiyono shows disinterest. She then insults Mizuno, particularly about her femininity and bra choice, and shows everyone catalogues of more kinky underwear. Kiyono argues with Nayu over looks vs comfort, but feels some embarrassment when the topic of who she loves is brought up.
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.
