When I opened my eyes, her large breasts and buttocks, exposed by her yukata, were only 3 centimeters away from me! HUNTB-636

On my parents' first family trip after their remarriage, I shared a room with my stepsister! She's a terrible sleeper, and her yukata accidentally opened, revealing her breasts and underwear! She even rolled over and faced me! Of course, I couldn't resist, and I cautiously started touching her, but unexpectedly, she became aroused! I only intended to touch her gently, but it resulted in her needing my penis! And so, in that atmosphere, we crossed the final line...