Sulu's brows raised a tick before entering the room. He was going to have to give more attention to learning Russian.
"Yeah .." He hesitated slightly, before giving Chekov a small and greatful smile. "I just wanted to say thank you. For watching out for little me. I really do appreciate it." He gave a slight, sheepish chuckle. "I remember the stories of how hyper I was so thanks for putting up with that." His words sincere, calm, even if with the tiniest embarrassment.
In Sulu's mind they'd only been a team for a little while. He'd just seen them all not too long ago and was still processing that they'd all been in this place for months. Had bonded, were bonding, and this sort of thing was more automatic for them that it was for him. Not that he wouldn't risk his life for any of them, had for the Captain would for any other of them. However ... changing diapers? Running after a hyper-child. As nice as he was, as much as he tried to stay calm under-fire, there would have been some major hesitating over the first two.