Haramase Taiken Gakushuu ~Shizen no Naka de Seikyouiku!?~

One summer, the protagonist is invited to join his aunt and her daughter in a seminar in the wood. In order words, a camping trip. However, when they arrive ...
"We are going to have sex education. Let's make lots of babies that will support Japan in the future."
It seems they signed up for the wrong seminar, but his aunt thinks that the lecturer's words are quite reasonable, so they decide to stay. And so, the happy 24 hours together with 2 pairs of mothers and daughters begin.