Ahhhhh bummer. I came over to say it wasn't working for my Mac but that explains it :(
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If it helps, from https://github.com/corwin-of-amber/nw.js/releases/ you can download the zip file nwjs-v0.70.0-osx-arm64.zip unzip it and you'll find nwjs (The engine behind RPG MV) working on Mac M1.
Download the KanjiCombat from here
right click on show package content on KanjiCombat select and copy all the files in Content/Resources
Now then again right click on the nwjs executable and show package contents, right click on the Resource folder and paste 6 items.
Now you should be able to play by clicking on the nwjs file; you can delete the original KanjiCombat.
The first time you might need to do right click/open if you get the "this software is downloaded from internet" message.