You help, to your regret

You cringe a little thinking about wrapping your hands around a dick, but you try to tell yourself its okay because Sam is your girlfriend. "Ugh... Alright fine, I'm not gonna let you deal with this alone baby."

Her face is still confused, but she relaxes in the slightest. She looks down at her new member, and untucks her balls from the small panties. They certainly are big, as you watch their weight flop out of the fabric. Now her cock is standing at full attention, and you get closer to her in order to start.

You reach out with your hand and touch Sam's new cock, unfamiliar with the receiving end of this. Her cock is soft, and you can tell she's sensitive when she moans slightly at the smallest movement. You begin to grip more of her meat, and start stroking up and down in the best way you know how, which is quite tiring for your arm considering her length.

Minutes of this go by and you can hear Sam breathing heavily, so you know that she's close. She closes her eyes in embarrassment, and she doesn't even tell you when she starts cumming. She just bites her lips, grunting and apologizing between spurts.