The sister is not shy with her brother - he has known and used her body for a long time. She often bailed him out while he didn't have a steady girlfriend. Now he has a girlfriend, but he enjoys pleasing his little sister. And he always comes only in her mouth - she loves the taste of sperm.
The Japanese girl squeaks, but obediently lets herself be pawed. These noises only encourage the guy to stick his dick in her mouth and make her suck him. Groaning and sucking, she turns him on even more. Oh, I'd love to put a pepper up her ass. That's the kind of cat you should let your friends roast too.