Bonyuu Club -Otona no Milk Time-  

 母乳倶楽部～大人のミルクタイム～

Hitoshi is just a white-collar worker. One day, he finds a strange shop sign when he is on his way home. The sign says "Preschool for Adults". "Preschool for adults? What is it...?" he he looks at the sign, a girl talks to him. She works at the preschool and misunderstands that he is a new student. She forcibly takes him to the room and they go inside.... Yes, some adults in preschool uniform play with teachers.... It is actually a preschool for tired white-collar workers....