Disclaimer: I don't own any characters or concepts; they belong to their respective creators.
Note: All characters are written as older than 18 years of age.
Cormac's hand slides beneath Potter's towel. The captain of the Gryffindor Quidditch team swears, and tries to pull away, but Cormac grips his shoulder with his free hand, holding him in place. Under the towel, Cormac's hand rests for a moment on Potter's thigh.
"Let me go", Potter growls, his eyes sparkling angrily.
Cormac smiles back, unperturbed. He knows that it's too late for Potter to do anything but ride this out. Cormac's hand slides up Potter's thigh, making the Seeker squirm. Potter glares at Cormac, but the Keeper ignores him. Finally, his hand touches what it has been searching for, and Potter gasps. Slowly, Cormac curls his hand around Potter's cock. He can feel the flaccid member begin to harden under his touch. Like any one man, Potter doesn't even need actions — just one touch is enough to arouse him. When Potter's cock is fully hard, Cormac begins to stroke it.
"This is one of the benefits of me being Keeper", he murmurs, bringing his mouth closed to Potter's ear.
Cormac gently bites Potter's earlobe. The Seeker jumps under Cormac's touch, but the Keeper also hears Potter's barely audible moan. Cormac smiles to himself, pleased at how easy it is to get a response from the Boy-Who-Lived. He continues to stroke Potter's cock — fast enough to keep Potter on edge, but slow enough so he doesn't cum.
As Cormac expects, it doesn't take long for Potter to surrender. His hips buck up, trying to get more friction on his cock. Cormac has been expecting this, and moves his hand with Potter's movements, denying the Seeker any extra pleasure. When Potter stops thrusting, Cormac resumes stroking him at his measured pace.
Before long, Potter's eyes are half-closed, and he's covered with a sheen of sweat. Cormac licks the Seeker's jawline from his ear to his chin, then bites Potter's lower lip. The Quidditch captain mewls into Cormac's mouth, but Cormac doesn't relent.
"Please", Potter begs under his breath, "let me cum!"
Cormac's finally acquiesces. His strokes quicken, bringing Potter closer to the edge. Before long, Potter cums, his seed staining his towel. He leans back, recovering from his orgasm. By the time he opens his eyes, Cormac has vanished.