Based on the adult manga by Satou Kimiatsu.

Shiraishi is a student who does not have much money. She sold herself to earn a lot of money and buy an Smartphone. But while doing her sex business in the Toilet Men, Shiraishi was caught by Chairman of Intra-school organization (which abbreviated OSIS) for her actions and threatened Shiraishi to work in a club that was run by the Chairman of OSIS.

(Source: Translated and Edited from Nekopoi)