[寝取られ注意!]俺に想いを寄せているらしい可愛くて無邪気でピュアな義姉が友達DVDに寝取られた

When my parents were transferred overseas, I had to stay at my friend's house. That's where I met up with my cute, grown-up stepsister Yui after not seeing her for a long time. I was attracted to her naive and innocent nature, and we gradually became good friends. But one day, she started to avoid me... I started getting suspicious, and I later saw her getting fucked by my friend...