It might not be as soon as Kisame thinks, but at some point it'll show. Not that Rui doesn't already think -hope, she's grown stronger since their last spar. Nothing would be worse to her than to show she hadn't.

She was tiring, it was expected, still she pushed to keep up even when she hit that point where it was probably better to slow down and catch her breath then keep going. But as much as she would like to remain his running companion Rui does eventually slow. Careful not to fall into a dead stop after maintaining such a pace for so long.

She doesn't expect him to slow with her, he had pressing things to do if they were to get that spar and maybe a decent mission. So she only offers a quick silent wave as she falls back, the stitch in her side well worth the jabs of pain as she breathed. The slower pace would at least allow her the chance to recompose herself before entering the village.

Rui was just sad that slowing down would mean losing his companionship.