If his pants or underwear are a lost cause after this, it's a sacrifice he's willing to make. He's definitely not thinking about it after Yuri makes an impressed noise at his cock. To be fair, it's actually pretty impressive, which is probably not particularly comforting at the moment. (There's maybe a reason he wears pants for his costumes, in fact.) He knows any comfort will be rejected, so he doesn't bother, just shifts them both so Yuri's positioned better on top of him, and then just hands things over to him.

"Go as slow as you need to. It's not a race. I don't want to hurt you," he says it, he means it, but they both know that that's absolutely 100% not what's about to happen. Since when has Yuri ever in his life done something either slow, or cautious? It would be a shame to start now.