By happenstance, class president Saori Igarashi catches Haruka and his younger sister Kanata in what appears to be an incestuous moment (while in reality it was only a slight accident with a milk carton), and henceforth tries to expose Haruka as the "pervert" she thinks he is. Haruka's desperate attempts to clarify the misunderstanding only adds fuel to Saori's hysteria, until Saori notes that after her last toilet session she has accidentally stuck her skirt in her panties, which Haruka tried to point out to her, and ends up recognizing Haruka's discretional nature...