My parents remarried and we went on our first family trip to a hot spring inn, where I shared a room with my sister-in-law! My sister-in-law is beautiful, has a great body, and a super beautiful ass! When we were sleeping next to each other, her yukata came undone, revealing her big breasts and panties, which got me really excited! And my sister-in-law's super godly ass was just 3cm in front of me! I couldn't hold back, so I pulled her panties aside and stuck my erect cock in her pussy, and when I came inside her many times, she got so excited that she started asking for my cock in return, and I ended up cumming inside her continuously without pulling it out!