The thongs that my sister wears are always provocative, exposing the wrinkles of her anus. She tempts me by showing off those wrinkles. While cleaning and stretching, I can't help but get an erection as I peek at the glimpses of her thong backside. I can't hold back any longer, so I spread her thong butt cheeks wide, stretching her anus, which gets me excited. She's a lewd woman who likes to be watched.