Nayu explains her situation to Keigo. Hiroki then comes over to Nayu's house to apologise and ask is there's anything he can do for her, inadvertedly offering to help her make an 'Underwear Appreciation Society'. Nayu also manages to convince Yako, Haruka and Mizuno to become members too. They hold the meeting at Nayu's house, where Mizuno is surprised to see Keigo, who was her senpai in high school. Nayu contemplates about love and whether she is adult enough to run a society. Keigo explains to Mizuno about how Nayu's grandmother helped her find confidence in underwear when she was in a bedwetting phase. The next day, Kiyono decides to join the Underwear Appreciation Society.
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.
