Witnessing my younger sister's masturbation, my rationality collapsed. She climaxed without realizing it, and I thrust wildly. (Yagi Nana MIDA-389)

"I saw it..." -- My sister's room was a mess and filthy. She'd been wearing the same unfashionable T-shirts since middle school. She was always on her phone, and her eyesight was terrible. In the end, she was a NEET (Not in Education, Employment, or Training) who stayed home and didn't work. A typical loser... Of course, since we're siblings, I had absolutely no interest. -- My sister was actually masturbating seriously! In that instant, my morals, ethics, and reason crumbled with a jolt. I became a lustful monster, aroused by my sister! My sister's hardened, loser-like cunt awakened! She repeated vaginal thrusts several times...