Yumi and Ryoko are close neighbors and best friends who always have plenty to talk about over tea. Lately, they've found themselves sharing concerns about their teenage sons, Kenta and Shinsuke, who seem constantly drawn to their mothers' desires. Yumi begins, "As mothers, I think we have a duty to properly educate our children about sex," and Ryoko immediately agrees. Before long, the two come up with a bold new idea. When Yumi says, "I have a suggestion...", Ryoko quickly responds, "I'm interested...!!"