Since her family was going to be away, I excitedly stayed the night at her house. Of course, we were being lovey-dovey, and that night, wanting to have sex, I gave her a passionate kiss, but she resisted. When I looked closely, I realized I was kissing her younger sister, Sana. I apologized immediately, but it turned out to be Sana's first kiss, so I was in big trouble. But Sana was blushing, and I couldn't tell if she was angry or sad...