Rimming is something that makes Flynn embarrassed. He'd been taught from a young age that that part of the body is especially dirty and not to be messed with, and when Yuri starts to prepare him he tries to pull away. Yuri merely glances up from between Flynn's legs and raises an eyebrow.
"It's dirty," Flynn complains sheepishly, and Yuri rolls his eyes at the cliché statement. "Relax," he says, and Flynn closes his eyes as his tongue touches his ass. It's a very odd feeling to have someone's tongue there, and he isn't used to it at all. Yuri licks in small, quick motions, then adds in longer strokes, and his tongue goes in circles that make Flynn's toes curl.
Sometimes, he thinks he'll never be used to it.
Yuri isn't shy; he does what needs to be done. He's that way in life, and he's that way in sex. He doesn't want to hurt Flynn, not in something like this. Injuries from sparring are one thing, but if he makes Flynn so sore that the blonde can't walk the next day, Yuri is determined it will be from his skill and not from lack of preparation.
No, Yuri isn't used to it either. But when it comes to Flynn, he'll do almost anything, and something like this is far from deadly. He doesn't even mind it, honestly. Flynn may claim it's dirty, but it isn't. Not really. Yuri focuses on the movements of his tongue, aiming to get some sort of reaction from Flynn even in something like this.
Most often he succeeds, but Flynn's face is still red from embarrassment when Yuri grins at him.