Mama no Undoukai 

ママの運動会

Kouhei works at preschool. He lives an extremely busy life surrounded by kids, but he is satisfied with his job there. He also enjoys watching their mothers looking forward to seeing their kids grow up. As he becomes close with the mothers, they tell him about their personal concerns. They are tiny complaints at first, but they gradually become something erotic such as, "about sexual relationship with husband" or "if Kouhei has a girlfriend?" His physical contact with them gets bolder day by day and Kouhei's libido gradually arises....