He is not keeping a lid on things. Or even if he was, the Soldier is kind of an expert at reading body language, nuances of tone, and the slightest change of expression. It's pretty obvious the kid's upset, and upset because of... what. Something they did or said? Being told someone wants his help?

This is beyond their skillset. Comforting is not a thing they're good at. For a long moment, they stare while Sora struggles with his emotion, trying to figure out the things they're supposed to do here. Hugging is right out. Their own little freak-out over cybernetics isn't far enough past for them to be okay with even a little touching. Words are what got them into this mess, to begin with, and they aren't entirely sure what the problem is, anyway. Why the kid is about to cry over wanting to help, being told he can help. That's the only thing the Soldier ever wants, so they're not sure how to fix someone having a problem with it.

(Well, what do you want, when you freak out at people?)

Pretending it isn't happening and offering a distraction, it is. The Soldier shakes themselves out a little, and says, still carefully quiet and calm, "Enough magic for now. And talking. Get out your knife, I'll show you a new move." Physical actions and focus on learning: good distractions from emotional distress. Right?