A high school girl's younger sister is dozing off with her panties exposed. Her older brother is excited by the sight of his sister's panties on, so he grabs his dick and starts jerking off. However, he is soon noticed, and although he treats his older brother as a pervert for lusting after his younger sister, he gradually starts to feel sorry for him. His younger sister is fed up with her brother's inability to cum despite offering to help him...!