I secretly fucked my girlfriend's busty sister who was too weak to resist pressure, and made her wet with my dick and sensitive and quick to cum

When I went to visit my girlfriend's house, who I've just started dating, she introduced me to her younger sister...I wonder if they're really sisters? Her personality, face, boobs (G cup), sex...everything about her younger sister is better than hers, she's just too good...I couldn't hold back and attacked her!