My sister started the popular "beautiful butt training" and made me help her! I could even see her pussy! I couldn't stand the sight of her thong ass sticking out, which was tightly digging into her! I pushed her panties aside and immediately inserted my erect cock! The training effect was so strong that I immediately ejaculated inside her! I thought she would get angry, but it seemed that my sister was also excited, and she asked for my cock in a vertical piston-like position! I was forced to cum inside her three times in a row without pulling out!