Written for painless_j.
"You're so hard," said Harry, his voice catching on an indrawn breath. "I... I didn't think you did this, really."
Snape smoothly rolled his hand over the knob of his cock. "No? That's not what you led me to believe. And I am a normal man, you realise."
Harry stared, licking his lips as that cock, shiny with a thick coating of lubricant, seemed to just come closer and closer. Though Snape hadn't really moved any nearer, had he... "I... yeah, I realise. Now. But Professor... uh, I feel a little uncomfortable watching you do this."
Was it just his imagination, or did Snape's gaze descend to Harry's crotch, then? "Yes, I can see that you do."
Harry felt his collar heating against his skin. Who would have thought the dungeons could get so warm? "I... you said detention, and this isn't... um, really appropriate."
"No?" Snape raised an eyebrow in what Harry could only regard as a challenge. "Am I correct in surmising that you will think twice before you refer to me, during class no less, as a 'wanker'?"
"Yeah, that's safe to say." Harry didn't know what he'd tell his mates when they'd asked what he had to do for detention this time. He sure wasn't going to explain that Snape had locked the office door and proceeded to wank right in front of him!
"Then you've learnt your lesson, have you?"
Harry nodded, though for some strange reason his own gaze was just glued to that cock.
"You may leave, then."
The man's voice was cool, but not cutting. Maybe that was what gave Harry the courage to murmur, "Do I have to? I mean... now? I'd sort of like to see you... er, finish."
"Ah." Snape's hand appeared to slow as he considered that. "You may stay on one condition."
"C- c- condition?"
"That you reciprocate."
Harry blinked. "You mean, let you watch me wank?"
He knew he shouldn't agree to terms like that. There was no way he wanted Snape watching him while he... but that cock in front of him was just glistening, wasn't it... He wanted to see Snape finish. He wasn't sure why he'd want that, but he did. He wanted it enough, in fact, to step a little closer as he looked down.
Enough to say, "All right."