Ai-chan is a devoted fan of her big brother, a sweet and obedient high school girl who agrees to anything he says. She always responds to her brother's requests with a smile, readily complying even with his most intimate demands. Today, as they engage in sexual "study sessions" together, she tries her best to resist his seduction, maintaining a firm attitude. Of course, it's their little secret—just the two of them, fully immersed in their private time.