Super Abnormal Petting: Abnormal Pleasure (1990)

Kotaro, a 40-year-old son who has quit his job, asks Yumiko, who he liked while working at the company, on a date. Then I went to an apartment that she rented with four of her female friends from her company, and I was made to be with her exhibitionist girlfriend, but she couldn't hold me. Since then, he has been visiting that room as he was told, and has begun to spy on Reiko, Hitomi, and Kasumi's unexpected play of affection.