The side story “After School Girl“ originally released in the series “Houkago!“ and scanlated by Yuri Project.
From batoto:
The principal’s valuable vase has been broken by the school prince and volley-ball club ace, Fujiwara-senpai. “Don’t tell anyone, I’ll do anything you say!“ Having witnessed the incident, Miu, on the spur of the moment, chose to go out with her senpai. Over the course of the dating, Miu became attracted to her senpai’s surprising frankness, but by then, it was too late to say her true feelings. This is how she came to fall in love with her senpai. A bittersweet highschool romance.