Synopsis: Himitsu no Jugyo

"What I'm going to do now...don't tell anyone, okay?" Shunta, a young man who lost his parents and was taken in by the Yuki family and lived happily with his new family. One night, he saw his adoptive parents having sex and when he woke up in the morning, his pants were white and wet. The pleasure that repeats every night - Mariko, the adoptive mother, notices this. And she makes a decision. "I have to...tell you..." In the middle of the night when everyone is asleep, a ``secret lesson'' for young men who are ignorant of sexuality begins...! ?