If you had not included your old sdmc/tinwoo folder you would not have it started in jap (until you changed the language in the settings page)
This is on a brand new freshly formatted sd card. Essentially a clean room install with nothing coming over between sd cards.
Here’s the play by play:

freshly downloaded from
https://github.com/mrdude2478/TinWoo/releases/tag/1.0.5

unarchived at top level.

new app dir is there

new app with sounds, images and new lang directory. Exciting stuff, this. (no .json at this level since it’s all brand new)

.json file in the lang directory.

looks to be EN. Let’s roll!

view of my brand new /switch directory.
I’ve only added:
- 90DNS tester to make sure I’m not communicating with Ninty
- 4TU App Store because I thought I could instal AIO with it (can’t BTW)
- AIO in order to pull the FW files down and extract the for use by Daybreak (he’s added Mega.no downloads!)

added the pristine GitHub copy of Tinwoo.

double checking that nothing has changed since we last looked. Yup…still clean. No extraneous .json files at this level.

There’s our .json in the lang dir.

contents of .json file…all good.
Japanese
WTF are you using google translation for? there's no need,
I use Google Translate via Google Lens to translate languages I don’t understand in real time. I’m not familiar enough with the layout of Tinwoo so I used a tool to help me find the Language button. It merely required the press of a button on my iPhone to solve the problem. Found the button and was easily able to change to EN (hence the comment “but wah” meaning it was simple to fix.) I didn’t think this was a WTF moment to be honest.
just remove the old config file or change the language in the settings page.
there was no old config. This was a clean room install.
In the post directly above where you posted, there's a link posted that contains pictures on what to do.
Much appreciated. You’re simply stating to do it by position. That works too.
If you were in some sort of scenario…
unnecessary comment removed. Just trying to help, man.