I can't believe I get an erection from my older sister's naked body (big breasts)! My sister took a bath with me for the first time in a while on a family trip, and my breasts were bigger than I expected, so my crotch was so hard that I couldn't maintain my rationality... 3

My sister took me out to the open-air bath on her first family trip in a long time. I don't usually think about it, but my sister's big breasts are more than I imagined, so I unexpectedly get an erection! Although she is trying to hide it, her sister is too defenseless, and she looks curious and brings her sexy body closer. I can't do it anymore, I'll be taken away if I find out! I was thinking that, but when I noticed my vagina was in, my sister reached out to my erect cock...