1-A

Through the recommendation of a rich man backing Aoi's father's loans, she enters a boarding school. However, the school is actually a place where the young girls are trained to the likings of buyers, and then sold!

Aoi is a member of the 1-A (anal) class. In this class, the girls are left as virgins and trained in the arts of anal so that their assholes become capable of any type of sexual play. Disgusted by the class, Aoi, together with her classmate Maho, slowly become prisoners of anal oppression.