All the other times Kirishima has flown before now, he'd been pretty confident he could survive a fall thanks to his Quirk. Not so much now. Feeling Ochako drifting near him does make him perk up further and put on a wider grin, half because it's her but also partially because he doesn't want her to worry about him, which he rightly suspects she is.

"Let's ride the rest of the way! We should figure out how quick the rides go now, right? Instead of when we might really need 'em?" Kirishima calls out after Ochako voices her options. Her hesitation between the options is making him get that she's deciding on whether or not to push herself. As much as they need to be speedy right now... he doesn't want her to push herself like this, where finding out how far she can go may result in them falling a long way. They can mess around with that later!

"What do you think, Yaoyorozu?"