The brother is taking care of his sister Mao who is sick with a cold. He is kind and brings her fruit. Eventually, the medicine seems to have taken effect and the sister falls asleep. The brother is excited by the sight of his sister sleeping. He starts masturbating while smelling his sweaty sister. When the sister wakes up, she sees her brother masturbating right in front of her! She is surprised and gets up. For a while, both of them feel awkward. When the brother tries to go back to his room, the sister asks him, "You were doing it, weren't you, big brother?" The brother shyly admits, "Y-yes. I'm sorry." After thinking for a while, Mao says, "Big brother, it's awkward if you keep doing this, and if you hold back, your sperm will die, right? Poor thing..." expressing her wrong knowledge and incomprehensible feelings. When the brother doesn't know how to respond, the sister shyly asks him, "Shall I cum?" The brother looks back in surprise. "What should I do?" The brother says he'll sleep next to his sister, gets into her futon, takes off his pants and underwear, and starts masturbating in the futon while smelling his sister's scent. The brother, who can't get off easily, asks his sister to show him her breasts. He still can't get off. She gives him a handjob, but he still can't get off, so she gives him a blowjob. The sister sees her brother and says, "We're brother and sister, so I can't put it in, but I can just rub it, so let it out." and starts intercrural sex. As she rubs it, she feels good and her pussy gets soaked, which makes her embarrassed. She desperately tries to suppress her voice. While she's doing this, his dick slides in. They both feel good and have sex in silence. The brother accidentally cums inside her.