My family is a single-parent household and not wealthy by any means, so we went on a trip to the hot springs just for the family. I was sleeping side-by-side for the first time in a while, and my sister, who sleeps in a bad position, had her yukata open, exposing her huge breasts! I never paid much attention to it before, but now my sister's defenseless huge breasts are just centimeters in front of me, and I can't help it! Before I knew it, I was squeezing her breasts and attacking her!