Today was my first visit to my girlfriend’s place. She lives with her older sister, who was supposed to be away on business, but a mix-up canceled her trip, so she came home. While my girlfriend made tea, her sister—accidentally or not—flaunted her perfect, round ass right in front of me. That night, I couldn’t sleep, her flawless ass haunting me. My girlfriend wouldn’t let me fuck, so I headed to the bathroom to jerk off but heard moaning. Following it, I saw Arisu’s room open—she was masturbating! I finally saw her glorious ass up close. She caught me watching but, instead of anger, pulled me in, letting me kiss her and fuck her. Unlike my girlfriend, she let me screw her anytime. We kept sneaking sex behind my girlfriend’s back while I maintained our relationship.