Eren stops running when Mikasa grabs his hand. This is the moment when he could be stubborn and try to chase the kid anyway... but Mikasa's right. He'd just make matters worse than they already were.

The warmth of her touch is a bit worrying though... but they do have the kid to catch. He can make her rest once that's over and done with if she still seems hot. He'd check her temperature too, if needed.

"Alright. I'll stay with the other two."