GS-207 - My sister walking around half-naked in this heat, she caught me staring and decided to tease me

It's a sweltering summer vacation, and my sister is walking around the house half-naked, driving me crazy. I tried to ignore it, but when she caught me getting hard, she started teasing me for being a pervert. Before we knew it, the heat and the tension led us to cross the line into an incestuous encounter.