"Hot," Merlin pants, bringing himself down. Arthur groans in agreement and tightens his grip on Merlin's hips, hands slippery. Merlin feels impossibly tight around Arthur’s cock, feverish and gripping like Merlin hasn't been stretched languorously. Arthur had insisted on taking it slow, air too warm and dry for hard exercises. That’s how they ended up with Merlin over Arthur, framed in light and heat, with a smile on his face as he slowly rides Arthur’s cock like he can’t get enough of it. Merlin looks utterly gorgeous, lithe and comfortable in his skin, chasing after both their pleasures effortlessly.
Some days, Arthur worries how obvious it is that his crush on what was simply a quirky shopkeeper has long stopped being a crush. These feelings caught him by surprise, sometime along their fourth month of dating, after four months and a week of fucking, when he started realizing how dully he finds time passing when Merlin isn’t around.
Today though, Arthur doesn’t care how obvious he’s being. Not when Merlin is straddling him, his back bowed in a perfect arch, brow brushing Arthur's hair and his mouth impossibly inviting in the shadows of Arthur's university room. They never flicked on the lights, and from the open window reaches noises from the street bellow. Dusty sunlight slides in from between half closed blinds to dance over their sweat-wet skins, illuminating the gleam of an eye, the flick of Merlin's tongue on his lips, the slick hint of the condom where their bodies join.
Arthur is already gritting his teeth and trying not to come too soon when he notices it. Merlin's nostrils look oddly red in the half-light, but constant movements doesn’t allow Arthur enough concentration to anticipate it happening until it’s too late.
It starts with only a single thin line of blood dripping next to the dip over Merlin's lips, stopping at his cupid’s bow. Arthur sucks in a breath. He knows this.
Since the heat settled in earlier that month, Merlin gets nosebleeds almost every other day. Arthur had been scared the first time it happened, and he still worries every time since: he cannot help the strong protectiveness surging inside of him at the sight of Merlin's blood.
But this time—this time, Arthur is simply turned on. His hips jerk up. Merlin's eyes fall shut, his mouth opens around a sound of pleasure that Arthur can’t even hear over the roaring in his ears.
Both nostrils are dripping now, one drop forming on the peak of Merlin's upper lip and shaking with each of their thrusts until Merlin shoves down harder and it drips onto Arthur. Another drop forms instantly, and this one is quicker to fall, followed closely by another. The blood looks extremely dark in the dusk of the room, only tinted red on the edges in the split second the droplets catch some light when falling.
Arthur swipes the next one forming with his thumb, smudges it over Merlin's bottom lip, daubing his cheek when a harsh movement of Arthur's hips makes Merlin’s head roll aside. Nothing has ever looked so hot to Arthur.
It’s not merely the blood, but how Merlin’s so into it he hasn’t noticed yet. It’s that Arthur could actually get this reaction out of Merlin’s body with his cock, hands and mouth alone. It’s how utterly gorgeous Merlin looks like this, completely open, shadows and lights shifting in his hair, his whole body contrasts on pale skin and messy crude smears.
Merlin's eyes flutter open and his tongue darts out to lick the path Arthur's thumb just traced. As suddenly as it had hit Arthur, he sees it hit Merlin as he takes the taste in, freezing on a downward shove.
"Arthur?" Merlin asks, his eyes falling on something on Arthur's face, then sliding down to his chest. Arthur can only imagine Merlin’s studying the dark spots that fell on him. The question makes him feel nervous, though he’s not sure why.
Arthur’s gaze drops to where one of his hands is still cradling Merlin's hipbone. Soft light shines on sweat and one of Arthur’s rings. Right beside it, Merlin's cock is flushed and engorged and looking almost as dark as the blood on his face.
This situation never happened any other time they've fucked. Arthur wouldn't have expected it to be such an aphrodisiac. Arthur is enthralled by the wet traces on Merlin's lower face, the way Merlin's thighs frame Arthur’s hips, and how his hole so sweetly pulses around Arthur even in stillness. He slides his hand up Merlin's side, cradles his neck, the faintest weight of his fingertips against Merlin's nape to encourage him to keep his head lowered forward. He doesn't want Merlin to accidentally swallow and cut this short. They'll have to do something to stop the nosebleed soon, pinch, breath, and stay still, but Arthur desperately wants it to wait a little. "Please," Arthur begs.
Merlin hisses softly, and Arthur looks back at his face. Merlin is beautiful, eyes hooded, wearing that shit-eating, cocky grin that had annoyed Arthur so much the first time they met— the same one that had made Arthur want to bend Merlin over his counter and have him right there in front of everyone in the shop on their second meeting. The one that could make Arthur do anything if only Merlin asked.
"Okay, yeah, okay," Merlin says, and bends down to meet Arthur halfway up for a kiss. It’s even messier than usual, the smell of blood heady and strong in the air. The taste blankets Arthur’s senses for a second, until Merlin pulls back for leverage and brings himself down firmly on Arthur's cock. Arthur muffles his whine with Merlin's collarbone.
They rut and kiss crudely, gasps raw and scrambling hands rough on each other. Soon, Merlin has blood smeared all over his lips and chin, neck and shoulder smirched with it, mouth looking wrecked. The glory of it all being Arthur’s fault makes him want to burrow even deeper in Merlin. Arthur has left those marks with Merlin's own blood, Merlin who’s safe, and unhurt, and doing this with Arthur, for Arthur.
Arthur swipes two fingers under Merlin's nose then takes Merlin's cock in hand, spreading blood there too and using it to pull hard. Merlin swears loudly, and in that instant, Arthur feels glorious.
They won't be stopping, not until they've seen this through. Not even now as their pace picks up and they are leaving faint dark stains everywhere. The air is heavy and smells of blood, sweat and sex, and Arthur has never felt so alive. A laughs bubbles out of him, and Merlin joins in.
They kiss, and when they part, their grins are smeared and their lips shine red.