My Beloved Sister-in-law, Who Raised Me With Her Own Hands, Was Cuckolded By A Lousy Friend... Mizuki Yayoi

Mizuki and I aren't real siblings. We met as step-siblings when our parents remarried during our school days. Several years passed, and after both parents died in an accident, we lived together, supporting each other. As we continued living alone together, I began to develop romantic feelings for Mizuki. My dream of staying with Mizuki like this was stolen by my best friend Kyohei. Kyohei, who has feelings for Mizuki, grew jealous of our relationship and, taking advantage of my absence, made a sudden move on Mizuki...