Shota, who is home alone while his father is away on a business trip, bumps into Satomi, a beautiful gal with a big ass and big boobs who lives in the same apartment building, and ends up in her room! Then, when he playfully touches her ass and boobs, he's in trouble! "My penis is swelling and stinging!" She has no choice but to calm him down with a blowjob. But Shota recovers quickly, and this time he shakes his sister's ass and has sex that puts adults to shame.