The air conditioner is broken and we're in a sauna! My sister-in-law overcomes the heat with a fan. But with a weak fan, my sweat never stops at all, and my sister-in-law lifts up her skirt in front of the fan, and even though she has no bra, she flapping her clothes, which makes me see her big breasts! I couldn't help but get an erection and my sister-in-law found out... It's insane! Just as I was thinking, my sister-in-law reached out to my erect cock! In the end, we were swept away by the atmosphere and ended up having sex while sweating!