My sister-in-law bends over in the bathroom: what a skimpy thong she's wearing... what an ass!

Imagine your hot sister-in-law is spending a few days at your house with your brother, and while everyone's having fun in the pool, you sneak off to spy on her. And you see her half-naked, wearing a thong, with that ass you've jerked off to so many times... Good fantasy, right?