NTR in the futon - The day my younger sister was creampied by her junior in the futon next to me

My younger sister Yui, who is a little older than me, has been a spoiled boy who has been sneaking into my futon since she was a child. However, one day, Yui brought my junior as her boyfriend. When the three of them sleep in the same room, they hear not a happy futon, but a sexy, hot voice... "What the hell are you doing in the futon...!" She hides in the bathroom, secretly cums inside her brother's futon, and has a lovey-dovey, creampie sex inside her. The little sister, who has been doted on, quietly wafts beside her brother.