Ikeda, who runs a gymnastics class, is visited by Miyori. She seems to want to get faster at swimming. "Nice to meet you. You're Miyori-chan, right?" Ikeda says, and Miyori replies timidly, "...Yes." When he asks, "I heard you're working hard at swimming?" she confesses, "I am, but... I'm slow. In PE class, I'm always at the back." Ikeda gently explains, "I see. But you know, speed doesn't come all of a sudden. First, it's important to build a 'foundation for your body.'" To Miyori, who looks puzzled and asks, "...Foundation?" he promises, "Yeah. Today, we won't swim, but we'll do exercises to help you get faster!"
As they proceed with warm-ups, stretches, and core training, Ikeda gradually gets aroused seeing the outline of her nipples through her tank top. He says there's an exercise to get even faster and has her change into a swimsuit. While imagining Miyori changing in another room, Ikeda starts instructing her on flutter kick practice and crawl arm rotations. However, his touches gradually become lewd, and he has her undress little by little, claiming he wants to see her muscle movements. Miyori, who has no knowledge of sex, has no choice but to obey what she's told.
"There's a drug called doping that makes you faster. Want to try it?" Ikeda suggests, and Miyori shows interest, saying, "If it'll make me faster..." Ikeda whispers, "My doping involves an injection, but the tip isn't sharp, so it doesn't hurt at all. It'll be fine. Keep it a secret from your mom." She naively nods.