He'd never gotten the treat of watching Stiles fuck his fist while his cock was buried in him. Oh, he'd gotten to watch him jerking off a few times, fist stripping his cock until he'd come on Derek's skin. He loved the look now, the feeling of those muscles grasping at him while Stiles spilled pretty over his skin. "Yours," he agreed hips lifting off the couch as he fucked up and into his mate, the base steadily growing thicker.
He knew what Stiles needed, not just the more he was pleading for, but the more that couldn't quite be vocalized. And his good boy, leaning forward so his cock stroked over all the spots he needed -- "Yeah, going to--" he thrust up, knot catching. One of his betas moaned at the sight, loud as he slowly worked his knot out one last time, and eased it back in with a moan of his own.
Derek tried to pull out, felt it catch again with a little whine and couldn't, not even with as slick as his cock was, slick that Stiles was still pumping out. "Hold on." It was a growled out order, and as soon as he felt both arms around him, he flipped them over on the couch and curled around his body, his hips giving short little thrusts that rocked his knot deep as it swelled larger.
Everything in him demanded he provide for his mate-- and his mate needed this. Pinning him down, he growled against his jaw as he went rigid, knot swelling, thighs tensing, hips shoving forward until he could get no deeper and came. "Fuck, baby," he almost whined as the tension fled from his frame and he started hose slow little motions that would keep them both coming.