Tsugou no Yoi Sexfriend

Arahama Yuu has 5 sex-friends. One day, his easygoing sex-life reaches a precipice. One of his partners, Shimizu Misako, who is also a co-worker at his company, had been sleeping with him on the understanding that they would marry. However, he only considered her a sex-friend, and even revealed the existence of the other 4. Incensed, she has him gather the other 4 together in his apartment.