You're on your way home after another long debriefing with Albus when you hear it; a soft panting sound. At first you dismiss it, walking swiftly down the hallway to the stairs, until a muffled moan makes you stop mid-stride. Soft light spills out of Lupin's room, the door slightly ajar, and your curiosity overrides your reason. The moaning increases as you creep closer with bated breath, watching from the shadows of the hallway.
Your cock twitches at the sight; Lupin is laying on his bed, legs spread, his hand tugging urgently on his hard prick. His face is flushed, mouth open and eyes squeezed shut, as he pulls himself off. Your heart pounds in your chest —you know you should leave— but your eyes remain glued to the vision before you.
Little moans escape from Lupin's mouth as he quickens his pace, his free hand sliding down to fondle his bollocks. You swallow roughly, your own cock pressing firmly against the constraints of your trousers. Lupin's hand travels further south, teasing his hole before pressing his finger inside. He whines softly, pumping his finger in time with his strokes.
Merlin, it's a beautiful sight. You want race into the room, drop to your knees and replace that finger with your tongue. You can almost taste the sweet muskiness, imagine how his hole would quiver under your touch. Your cock throbs at the thought of pressing inside of his tight heat, how good it would feel as his arse stretches to fit you.
Lupin's head tilts back, his hand a blur over his prick, and you can't hold back any longer. You press your hand over your aching cock —so hard it hurts— and thrust into your palm. The friction is incredible, your bollocks so tightly drawn you’re sure you’ll come any moment now. Lupin’s thighs tremble, his hips arching off the bed, and a harsh cry fills the room as he spills himself all over his hand. And then you hear it: your name uttered from his lips, soft and sweet like a promise.
“Oh fuck.” The words tumble from your mouth, your cock pulsing as you come in your pants. You don’t even realize you’ve spoken aloud until Lupin’s eyes snap open, locking gazes with you across the room.
You’re still shuddering from the aftermath of your orgasm, pants sticky and wet, with your hand braced against the doorframe for support. Lupin watches you cautiously, a mixture of shock and anticipation written clearly on his flushed face. Run, leave now. The command flashes through your mind as the realization of what just happened fully settles in.
“Severus…” He murmurs your name again, this time in invitation.
This is a terrible idea, utterly horrible. And yet… You take a steadying breath, walk into the room and close the door behind you. You’ve made some bad choices in the past but, somehow, this doesn’t feel like one of them.