[Alerte cocu !] Ma demi-sœur mignonne, innocente et pure, qui semblait avoir des sentiments pour moi, a été cocu par mon ami DVD

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...