Musabetsu Renai Bokutte Gangu? 無差別恋愛～ボクって玩具？～

Tomo, a university student, lives alone. One day, Aya, his older brother's wife, suddenly visits his house and robs of his virginity.... She threatens him to report the matter to his older brother and attaches a collar around his neck. She also tells him to keep wearing it for a week and leaves his room.... From that day, wherever Tomo goes, married women compel him to have sex with them. As a matter of fact, Aya posts a paper on the notice board of his apartment, "You can do whatever you want to this boy...." Though Tomo finds and removes it, Aya says, "Don't turn it down if someone tells you to do something...."