To blow him

Lexi put on a wicked smile. "Now be a good girl and thank your friend for coming here, and the times he had done something for you." You looked shocked at her. There was just one thing Mark did for you that Lexi knew of. "What are you waiting for? Get on your knees and give him a blowjob."

You didn't wanted to, but now that Lexi had commanded you, you couldn't help it. You knelt down before Mark and unzipped his pants. With your hand to search for his penis and found it resting soft in his underpants. Your fingers lightly rubbed on it to get it at least a little bit hard, so it could stand up on its own. Then you pulled it out of the pants. Mark's penis wasn't big at all. Compared to Lexi's it was really small, and even yours was bigger. But that didn't stop you from wrapping your lips around it. You began to lick and suck on it, like you had learned the hard way over the past days. Mark's penis was getting hard, but even fully erect it was just half the size of Lexi's. But even that was enough for you to feel grossed out.

"You know, Alice is quite the naughty girl." Lexi said and knelt beside you. "She may have been a boy, but she loves giving blowjobs and playing with her tits, that she even gets hard from it. Right, Alice?"

Your hands went to your augmented chest and started playing with it. Over the last few days Lexi not only let you blow her, she also made you play with your tits until you came. All the playing had made the skin pretty sensitive and your nipples quickly hardend. Playing with them felt even better than with your tits and within moments your penis reacted to it and stood up in your thong and skirt.

It didn't took much longer and Mark came. His load of cum wasn't even half as big as Lexi's and you had no problem swallowing it. But it also had another taste, sweeter and not nasty.

"See? Not so difficult to return the favor." Lexi said pleased with your work.