Part of Sirius wants to close his eyes and just sink into the sensation, give over and let Kieren feel every single bit of this, but Sirius is often selfish and he can't bear to look away away right now. So he keeps his eyes open, focusing intently on Kieren's expression instead, on his wide eyes and parted lips, the way he seems to have stopped breathing.

"Fuck." It comes out a harsh grunt, Kieren's strangled moan slicing right through him and he feels his back bow as he pushes himself closer to the brink, his grip tight, legs shaking. "Fuck, fuck, I-- Kieren."

It crashes over him then, cock pulsing as he spills over his fingers and Kieren's chest and belly, painting his pale skin in streaks of come.