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

Original title: 押しに弱すぎる彼女の巨乳妹とこっそりハメて僕のチ●ポに沼らせて敏感即イキ早漏体質に仕上げた

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!