The siscon brother who came along because he was worried about his sister saying she wanted to go to the open campus in Tokyo. Of course, they're staying in the same hotel, but in this non-ordinary space called a hotel, despite her being his sister, the situation of being alone with a girl makes him restless and excited! It seems his sister was feeling the same way, and they both became aroused, leading to him penetrating her vagina with his penis! They had vigorous sex!
