He makes a face like a grimace at that--not disgusted by the suggestion, but complicated, aided by the long drawn out "Nooooooo..." that comes with it.

And then a deep sigh that slumps his shoulders after that.

"She's...we're..." Um. "We're from the same world. I was her guardian, and we were close. But...it's been two years since we've seen each other. I said I'd stick with her no matter what! ...but."

It's a surprise why his voice even brightened earnestly in that moment at the end there, the way it then drops with the sagging of his posture, his shaking head.

"I don't regret coming to help, but...I dunno. Maybe I do? She was happy to see me when we got together again, but."

But the one easy way to make Tidus an unsure, uncertain mess: Disappointing Yuna. He's even rubbing the back of his head.