Assuming Gai let him off the kiss enough to do so.

As much as he wanted to strip Obito of his clothes, and as much as Gai was trying to, he also wasn't eager to break the kiss again, not when he could kiss his squirming boyfriend and put his hands all over him and enjoy Obito enjoying this.

He unfastened Obito's pants and, heart pounding excitedly, he slid his fingers down under the clothes, along Obito's warm flesh, first just his stomach and then down into his pants. Gai's cheeks flushed, a bit embarrassed, and very turned on, by his own boldness.