Nayu Hayama, a middle school student, surprises everyone when she trips at the school entrance ceremony, and, thanks to a well-placed Panty Shot, is revealed to be wearing lacy underwear unfitting for someone her age. It's revealed that Nayu's older brother Keigo is an underwear designer, and Nayu herself is a a fan of all things undergarments. So she decides to help her fellow classmates be more knowledgable by creating an Underwear Club in school, and recruits two best friends, Yako Jinguuji and Haruka Shiraishi, in with her. Nayu's indefatigable enthusiasm sweeps up a worldly girl (Kiyono Amahara), a busty home-room teacher (Tamaki Mizuno-sensei) and a flustered boy (Hiroki Komachi).