Living with his stepsister, his younger brother falls in love without realizing it

Ai-san and I are not siblings. When I was a student, Mr. Ai was the son of my father's remarried partner. A year later, after my parents passed away, Ai became my parents. During the days we were alone, I felt a special love for Ai-san, who was my only family member. Just when I vowed to make Ai-san happy in the future, my bad friend Shinji approached our family. “Your sister is quite sexy and beautiful.”