Original title: 人妻スイミング倶楽部
The protagonist starts working part-time at a swimming school during summer. And working alongside him are lonely married women who are excited at the appearance of a young man.
Noticing that the business isn't doing so well, the protagonist proposes changing swimsuits to something more revealing. While embarrassed, they decide to go through with it anyway.
And so, his everyday life surrounded by tempting women begins.