Today my girlfriend's parents were out, so she invited me to stay overnight at her place. The thought of sleeping with my girlfriend and having sex with her that night made me feel excited. Unable to resist any longer, we had sex before anything else. I wanted to have raw sex and ejaculate inside her vagina, but she insisted on using a condom. With no other choice, I put on a condom and we had sex. While we were passionately engaged, suddenly her sister walked in, caught us having sex, quickly apologized, and left. It turns out her sudden return was due to the canceled appointment today. Her sister Non is an incredibly beautiful girl, especially her big breasts that no man can take their eyes off. After chatting for a while, my girlfriend went to shower, and Non approached me, pressing her breasts against me. "You can ejaculate inside my womb." I couldn't resist her invitation, so whenever my girlfriend was away, Non and I would engage in sexual activities, continuously ejaculating inside her womb, until... my girlfriend came back early and discovered everything...