Yumemiru Otome

Overview

Manaka is in love with the handsome teacher Tonami, whom she admires, and Mizuki gently watches over her younger sister. The sisters thought that their sweet and bitter youth would continue like this, but...? When Manaka confesses to Tonami that she will do anything for him and wants to go out with him, everything changes! In exchange for going out with him, Manaka is at Tonami's mercy, and one day she is surrounded by strange men who are Tonami's "friends". The men who surround the frightened Manaka make her immerse herself in hellish pleasure...? (Source: Lune-soft, translated)

Source: AniList