He should get on board - they both should get on board. But it's not really the greatest situation, is it? He shouldn't have to, none of them should, and either it's that or the nerves of the guy that makes Tidus hesitate, frown as he looks back at the train and then grunt, rubbing the back of his neck.

"Sure, but..." But... mhhhrr. He looks back at Prompto, and tries for a more decided expression as he nods.

"Hey, no matter how weird this is, I'll help you out, 'kay? I'll tell you anything you want to know. So...I guess I can take you to where all the drinks and the mountains of cookies are, if you're into cookies," he offers jokingly.

(But also not jokingly.)