Friend's Younger Sister's Panties

So my friend's family has been going on at least one trip every summer for the past three summers, and they always ask me to watch their house and animals for them. I like my friend and his family, so of course I do it for them because I get paid too. That is not the only compensation I get for watching their house though!

My friend has four younger sisters. The oldest of his sisters is 15 and is absolutely beautiful. She is slender, with an athletic build, perky A cup boobs, a nice toned butt, and legs to die for (she is a distance runner, so her legs are GREAT!)

So every trip my friend's family takes, I am sure to make at least one trip to his sister's room and snoop around for some panties. This most recent trip I made was earlier this evening, and I found a sexy pink pair of panties that were used, but not fresh. They had what appeared to be white cum stains in the crotch which really turned me on. About all of her used panties have these stains in them and I am convinced that she masturbates in her panties and then discards them in her hamper.

I took those panties and sat down on the chair in her room and jerked off twice into the crotch of her panties, and put them back in her hamper, hopefully for her to find when she returns home from her trip.

I plan on making a couple more visits to her bedroom before her family returns in a week.