Trying to guess what Yukio was trying to say seems too likely to end up going wrong, making him feel like he's not being understood or has to go along with whatever Ginko thought he might be asking.

So he stays quiet instead, right where he is, and waits. If Yukio does want to leave, he should be able to whenever he wants; if not, he can stay there. And, if he finds his voice again, Ginko will listen to whatever he wants to ask.