It's been a while since our family trip. Taking a bath with my sister, I saw her naked body (big breasts) for the first time in ages, and it was too stimulating for me—I instantly got an erection! But there was no way I could let my sister find out, so I desperately tried to hide it… but she found out anyway. Bracing myself for her scolding, suddenly my sister's hand was on my crotch! Why? My sister kept pressing closer as I panicked.
