When you’re small with 〜うちは

Grammar Explanation

ふらいんぐうぃっち » Volume 5 » Page 49

During a visit with Anzu’s family, Makoto receives a request to babysit for another witch. Things are fine at first, but after a while, rain begins to pour inside. Anzu’s mother realizes that the child they’re watching over has rain magic.

“You don’t have control while you’re small, right? When he’s uneasy, it pours like just now.”
“I see. So that’s it. It’s a little scary suddenly being in a place you don’t know. You’ve been patient, haven’t you?”

Here, うちは is contrasting when one is a child, versus when they are older and more in control of their magic.