Hi there bud!
Hmm. GameTranslate does unfortunately not at the moment have a mode that supports vertical text. It is on my todo list, but I would expect it to take a bit of work since everything is built to read and adapt to horizontal text..
I am very curious on how this problem could overlap to other languages however. Do you mind taking a screenshot of the problem you're describing when you're not capturing vertical text?
And oh, don't worry about being negative (you're not), I'm more than happy to receive feedback and what works and what doesn't. There's endless edge cases, languages, right to left, left to right, horizontal text, vertical text etcetera. It is extremely time consuming to test everything on my own. So I am grateful that you're giving input! :)