Peeping on My Girlfriend Fucking My Brother

Kaito and Hibiki are a happy couple. They spend time together, and sometimes even get down to business at his place... where Hibiki can hear Kaito's older brother having loud sex. To the dissatisfaction of Hibiki, Kaito isn't aggressive in bed. One day, Kaito has to go to work instead of on the date he promised Hibiki. She steps out of his room, thinking she should go home, but bumps into the older brother who is butt-naked. Her eye and mind start to wander as the brother makes a pass at her... Is her relationship strong enough to withstand his advances?