The guy is lucky with his sister - she is a nipple. She's ready to open her mouth for him to stick it in her. Apparently she serves him regularly, because he no longer feels affection for her, but fucks her like a street whore - rough and bold. However, she seems to like this treatment.
Such team-building group therapy sessions are very popular in Japan. This time the Japanese went to a group oral sex session, where the team has to demonstrate coordinated work and bring a woman to orgasm in the shortest possible time.