Due to my parents' remarriage, I suddenly started living with my younger sister today. At first, I just thought she was cheeky and cute, but she gradually started to tease me because I was weak-willed... "Hey, hey, big brother! Let me play with your nipples in the morning!" My sister just loves my nipples... I got turned on by her constant teasing of my nipples and it became irreversible, so there was no point in worrying about it, so this is the story of how I fucked her like crazy for three days.