Hello, hello! Translator here quickly chiming in about Wellmy and Iora's secret identities!
I'm always for keeping the original nicknames, but we unfortunately did have to go for something a little different from the Japanese for a couple of reasons.
For Iora, I simply chose to romanize her Japanese nickname (アロイ, aroi) as is. It does make it Iora backward in English, which I thought was an added, silly bonus.
As for Wellmy, she actually uses the nickname Zumiano gave her (ミィ, mii). We (as in Emlyn the editor and I) concluded in Vol. 2 that we sadly couldn't keep it. Spelling it as "My" looked a little jarring, and it could've made some sentences hard to understand at a glance, and "Mii" was too far from her original name to really be an option. The Japanese version of the book has Wellmy's name romanized as "Wellmy" on one of the first illustrations of Vol. 1, so spelling her name differently preemptively wasn't an option either. That's why we settled on "Wellie," as it felt like something Zumiano might come up with.
Since she uses the nickname Zumiano has given her, her identity is obvious from the start, so we chose to keep it the same.
Hope that's a satisfying explanation!