Kabuto really was a terrible kisser.
His movements were all responses, not aggressions, and sometimes he responded a little too much, if that was even possible. For a top-notch spy of his caliber, when he let his guard down and dropped the act, he was as easy to manipulate as a tiny seashell caught in a rip current. He was all soft throaty moans and clutching at clothing for balance and arching into every touch like each sent shockwaves throughout his body.
It couldn't be plainer that he hadn't the slightest idea what he was doing, though he was clearly trying to be a fast learner in this department as he was in most others, bless him. He could usually anticipate when to tilt his head and when to part his lips, all little things that he had down to a science, things he could measure by psychological or physiological means. But when he became impassioned he also got clumsy, struggling with his master's admittedly challenging tongue and not knowing what on earth to do with his hands except hold on for the ride.
He couldn't exactly be blamed for how inept he was, but Orochimaru still chuckled at the boy and how frustrated he got when, for once, he simply wasn't a natural at something. Kabuto was talented at clinical things, but once emotions and passion came into play he was left floundering. It was cute, in a way.
Orochimaru didn't mind his lack of finesse. Kabuto always tasted delightful; there was a slight salty flavor to his mouth that the Sannin liked enriching with a spot of fresh blood drawn from a bitten bottom lip, and those lips were so warm and soft that it was hard to take any issue with how sloppily they could sometimes move. And each little gasp and whimper, each sound that no one else could evoke from the medic, was music to Orochimaru's ears.
Kissing Kabuto was not an activity he partook in seeking to be impressed, anyway. It was something he preferred to simply savor and enjoy, and Kabuto was good, at least, at giving him that.