"Sure, no problem." He shakes his head, but he nods once. "I won't tell. But, even if he's from the future... but you know more about it right now than him? How is everything?"

Since Bulma went. And even if it's a conversation to stay between them, Tidus can't help but have some concern for the place Trunks came from. Where he might return.

It's related to Trunks, so he cares.