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]