Just before we started living together, I was allowed to stay at my girlfriend's house until the day we moved into our new home. She had a quiet older sister, Ura-san. Ura-san, who seems strict at first glance, was completely defenseless at home. Her H-cup breasts were shaking without a bra, and her tight camisole was showing signs of nipple pain... Just when I Ito I couldn't stop getting an erection from Ura-san, she started seducing me...!?