Shounen to Tomodachi no Mama: Naisho no "Nakayoshi Gokko"

One day, Haru was going to a sleepover at his friend Kouki's house. When he got there, he met Kouki's beautiful mom. The boys were going to sleep soon, so they went to take a bath. Wait... Kouki's mom is gonna go in with them?! Their secret bathroom playtime was about to be the first of many happenings that would change Haru's life completely... [Translated from DLsite]