Incest is forbidden for one day only! HUNTB-682

My sister has recently grown into an adult. When I saw her casually exposed underwear and her sweet breasts, I couldn't help but get an erection! Then he said, "Bro, maybe I'm the one arousing you?" I couldn't help but think, "You're aroused for me too!" It even got to the point where he retorted! It's true, I've had erections before as a virgin. But my sister is my sister, and she seems to be aroused by my erections…