JUL-920 My beloved sister-in-law, who raised me single-handedly, was cuckolded by my worst friend... Nao Jinguuji

Nao-nee and I are not real siblings. My older sister Nao was the stepchild of my father who remarried when I was a student. Later, after my parents died in an accident, Nao-nee, who was a lot older than me, became my parent. Living together was lonely, but I also felt happy because I was in love with Nao-nee. One day, my best friend Yuzuru was secretly talking to Nao-nee, and I felt jealous when she approached her.