It's true that I neither speak nor read Japanese. In regard to English, I could be considered over-educated. That said, these seem like pretty good subs to me. They match up quite nicely to the audio. They seem to be appropriate in context. They have only minor errors in grammar. Aesthetically, I suppose one could tweak the font, etc., some, but that's a presentation issue, not a content issue. Having started viewing anime in the late 1980s, I would have been ecstatic at subs of this quality back then and for many years after. Thank you ever so much for producing these. It allowed me to enjoy the OVA to a much greater extent. Now if there were a way to easily remove the watermarking, my viewing pleasure would be complete.

Maybe you could of put your effort into something more better than wasting your time on Mushin. Like this release here https://nyaa.si/view/1211863 which could use editing. This short is from the light novel of Arifureta volume 5 extra chapter: Sunny with a Chance of Thunderstorms https://nyaa.si/view/1168416 or https://nyaa.si/view/1175169

Too late, I hadn't noticed that other release exists. I pretty much retranslated 70% of it anyway. I'd say this script needs a quick tl check (mainly for the names of the days), one editing pass (fixing the grammar errors at least, if not improving the flow and the style), and fixing the timing (at least eliminating the weird gaps between lines, if nothing else). If I could be arsed, I'd read the light novel chapter and cross-compare if the days are the same ones, spend some time mulling over the editing, and open one of the timing guides to refresh my memory how this shit was done... but sorry, I can't be arsed.