"Who do you like better, my sister or me?" My girlfriend and I promised to get married and went back and forth between each other's rooms. I thought that such happy days would continue forever... Until that day... As soon as my girlfriend left the house on a business trip, my younger sister aggressively seduced me, and even though I felt guilty, I fucked my sister, who was sexier and cuter than my girlfriend, until I ran out of sperm. The days of sex with my sister were the most nasty, vulgar and exciting of my life during the three days my girlfriend was away.