IENE-433 My sister, who got dumped by her boyfriend, canceled a hot spring trip. I went in her place and ended up sharing a room with someone at the mixed-gender open-air bath!

My older sister brought her younger brother to a hot spring trip that was canceled by her boyfriend because it was a waste. She was supposed to go with her boyfriend, so of course she shared a room with a mixed bath. I Was Not Always Conscious Of Her Older Sister's Big Tits, And I Got An Erection! As she tries to hide it, her older sister approaches her, shaking her big tits. I thought that I would get angry if I found out, but my sister was involuntarily fascinated by her erection.