Focuses on the experiences of the heroines' first periods and also about the relationship between Nayu and Hiroki during the school excursion. A fellow student has apparently confessed her feelings to Hiroki during the campfire ceremony which was held one day earlier than scheduled, but he ended up rejecting her. During the treasure hunt, Yako felt uncomfortable since her first period started last night and Nayu volunteered to head back to the checkpoint to ask for medication that can relieve menstrual pains, but runs into Hiroki and he ended up piggybacking her to the checkpoint. And it seems that a possible coupling of Kiyono x Amane is on the cards in the final volume. Chapter 47 has Nayu decided to disband the Underwear Club since everyone has already found their separate goals, but her friends later helped her out of this. Final chapter shows Nayu's new short-hair look (the cover of final volume shows this in color), which shows her new-found confidence. And it seems like Nayu and Hiroki seems to have (in a weird way) started going out together.