Have him return the favour.

Technically, your job is finished. His soul is marked, but no one ever said you weren't allowed a little fun on the side.

"Glad you enjoyed it. I hope you were taking notes" you say.

"What do you mean?" he asks.

"Well, like I told you, it's a bro job, two dudes helping each other out" you say.

"Wait man..." he begins.

"Dude, if you don't do me then you're breaking the bro-code. I'm sure you don't want anyone to know you let a guy suck your cock. Bro's keep secrets between each other. I've just shown you I'm your bro, so now it's time to show it back." you say, your tone serious.

The guy stands motionless for a while, his cock still on display, gradually going soft as the orgasm passes. He seems to be looking you over, always lingering on your package, perhaps wondering exactly what he'll be expected to suck. Eventually he nods "OK dude, fair's fair I guess, but I swear, you tell anyone..."

"Bro!" you interrupt with an insulted tone.

He steps towards you, breathing heavily. Cautiously, he reaches out and cups the front of your jeans. You feel his fingers tighten slightly as he squeezes your bulge which is already somewhat engorged after working on his cock. He spends a while rubbing and squeezing and you're soon fully hard.

"You gonna let it out? It's getting kinda tight down there" you half ask, half command. He looks at you and swallows nervously. With fumbling fingers, he unbuttons your jeans, allowing your cock to push out, now only restrained by your boxers. He reaches inside the waistband and takes you out, eight inches standing fully hard and waiting. He begins to jerk you off, looking away from what he's doing. You enjoy the new sensation. Technically this is the first time you've ever experienced sex as a mortal and it's intoxicating. You stand and let him work until it's clear he's delaying the next stage.

"OK, I'm ready" you say. He looks at you silently, his face anxious. "Come on man, fair's fair" you say. After a moment, he kneels down before you. A few more moments go by until finally you feel a warm, wet sensation spread over the head of your dick. You look down to see him tentatively sucking on the tip of your cock. "See" you say "It's not that bad, right?". You reach down and gently pull his head towards you, your cock sliding further into your mouth.

It's obviously the first time he's had a cock in his mouth from the way he inexpertly sucks and bobs his head arrhythmically, but you enjoy the novel sensation none the less. You begin to thrust your hips and finally the guy seems to find his stride. The feeling of sliding past his tight lips, the soft inner of his mouth, the slight roughness of his tongue is glorious. You begin to breathe heavily as the climax begins to build. Suddenly he comes up off your cock "Dude, don't nut in my mouth" he asks in a pleading tone.

"Fair's fair" you snap back, and pull him back onto your cock. He initially resists but begins sucking once again. Finally, a wave passes through you and you feel a release of tension. You hold your partners head in place while you cum in his mouth, releasing him once the last spurt has left you. He quickly turns and spits out your load into the toilet and you hear him retch a little.

"Sorry dude, I guess it's been a while" you joke. He looks up at you, still shell shocked from his first taste of cum. "You OK?" you ask.

He nods "Yeah, I've just never..." he begins.
"Yeah, it's an acquired taste" you tell him smirking. Having concluded his end of your little pact, he leaves the bathroom. "Catch you around" you say.

"Yeah...sure" he says as he leaves to return to the party.