"Are you sure those are for you?" Scott asked suspiciously as Stiles lifted a pair of 40lbs hand weights off the floor of the local gym/sportswear shop.
"What. These?" Stiles looked back at his friend, putting down one of the weights to grab onto the other one with both hands. "Of course. Derek said I should start working out, because he thinks I'm too skinny to fight the Alphas off." He scoffed loudly as he dragged the weight to the counter. "Not that he's right, of course, but if that makes him sleep at night…"
"Why does he even care about your muscles?" Scott asked as he lifted up the other weight and carried it after Stiles with natural ease.
"That, my friend, is the million dollar question. But I guess it has to do with my googling superpowers. What would you do without my help, anyway?" He handed the money to the wide-eyed girl behind the counter (who was two years their senior and knew perfectly well that Stiles Stilinski and sports went as far as bench warming for the lacrosse team). "And we all know how much he wants you to be safe," he continued. "And as you are incompetent on your own, I'm not allowed to die on you. Thus, I'll work out at home." He put the hand weights in Scott's hands and guided him out the door with his hands on both of Scott's shoulders.
After working out for two months, twice a day - because apparently that's what's going to give you well-defined muscles, as Danny was nice enough to elaborate on for Stiles, because, damn, have you seen the dude without a shirt? He has a six-pack. And Stiles is man enough to admit that it was hard even for him not to stare at Danny's abs. So after two months of sweating twice a day he started seeing signs of his changing physique. Some of his shirts were a bit too tight around his biceps and thanks to Danny's advice -again- to do sit-ups too, his abs were actually there. And sometimes it was really hard not to just stand in front of the mirror that ran along the wall of his room next to his bed. So this is how he found himself half-naked one Saturday morning after a work-out session, staring at his own reflection, hands running absent-mindedly over his arms then his stomach.
Derek hated weekends. It meant that everyone stared at him when he went out shopping because, apparently, the dear citizens of Beacon Hills thought that he didn't need to eat food and he was able to live only by consuming sunlight.
He hated this Saturday especially, because after talking to Chris Argent about his -and Peter's- plans about how to prepare themselves against a very probable attack of the Alpha Pack, he had to visit Stiles, because he wouldn't go to Scott after he declared himself not part of Derek's pack. So Stiles was the only one who could tell Scott the news.
Derek knew that the Sheriff won't be home, as there was a traffic accident somewhere in the district. So he wasn't surprised that no answer came when he knocked on the door of the Stilinksi house. He could hear music playing on the second floor where Stiles's room was, so he tried turning the knob. It was open. The Stilinkis were clearly at full alert and prepared against sudden attacks. Not that a pack of Alphas should count as danger, no.
He let himself in and waited a few moments in the foyer, but Stiles obviously didn't hear him. He climbed the stairs and followed the music to Stiles' room. But as soon as his foot left the last stair, he had to stop. And just breathe. Something was different. He couldn't tell what it was, but it came from the same direction as the music.
He went -sneaked- towards the door and stopped to peep in. He could see clothes lying around on the floor and could hear Stiles on the other side of the room. His nostrils flared as he breathed, smelling Stiles' personal aroma stronger than ever. He carefully pushed the door open a bit more and saw Stiles.
Half-naked. In boxer briefs. Swaying his hips to the rhythm of the music as he stood in front of a huge mirror watching himself. He didn't see Derek opening the door and continued what he was doing -stroking himself. Derek knew it wasn't really stroking, but he couldn't think of it any other way. Stiles hands ran around his hips, one hugging himself from the front, the other from behind. His underwear was darker around the waistband, sweat coloring it to a darker shade. Derek dragged his eyes away from Stiles' hips and let them roam over his back. The boy's -because that's what he was, just a boy, Derek told himself- spine stretched beautifully, surrounded by glistening muscles from each side. As his eyes skittered even higher, he could see a drop of perspiration run down from Stiles' neck towards his hips, zigzagging between his shoulder blades where his skin broke into goosebumps.
Stiles moved his hand from his waist towards his arm and ran it over his now muscular biceps then down his forearm until he rubbed his palms together, smoothing the sweat on them.
Derek licked his lips as he stood there, breathing Stiles in and fighting his wolf, stronger with every breath he took. He could feel his teeth -fangs- elongate and he ran his tongue over them carefully, closing his eyes as another wave of Stiles' perspiration hit him.
Before he could stop himself he let out a small noise, something between a growl and a moan. Stiles suddenly turned around and looked at him with wide eyes.
Derek felt his wolf banging against his restraints as he looked Stiles over from his bare toes up to his head, taking in his lightly-haired calves, thighs and -oh.
Oh.
His hand, that was massaging his morning erection.
His wolf, having finally identified the unfamiliar smell of Stiles' precum, broke free and took over, forcing Derek to take a step closer and shut the door closed behind him as he entered Stiles' room.