One day, when I went to my girlfriend's house to play, her cute little sister, Natsutsuki, greeted me. Natsutsuki, who has obviously bigger breasts than her older sister, seduces me by showing me a glimpse of her breasts without a bra! She suddenly asks me to make a baby, not to date her, saying, "Please do something about the rumbling in my uterus!" I get excited by her horny body, eager to get pregnant, and even though I know it's wrong, I get an erection and secretly keep milking my semen without her knowing!