Ushinawareta Mirai o Motomete

Uchiham Academy has seen an increase in the number of students in recent years, which led to the construction of a new school building. The story goes back to the last festival in the old school building. All the club leaders decided to do their best to make this festival the best in the school's history. Sow is a member of the notorious astronomy club, which basically decides various issues instead of the student council.

One day, he stays in the school infirmary until late in the evening because he slightly injured himself in judo club class.
Suddenly the building is shaken. Shocked, he runs up the stairs, where he thinks the epicenter is, and there he meets a mysterious naked girl who recognizes him at a glance.
The next day this girl, Yui, shows up at the astronomy club, expressing her desire to join.