It's basically the same as the 2021 Horimiya anime, but with simpler art and a more cut-back storyline. Technically, though, it's closer to the original source material.
Horimiya started out as a four-panel web manga (2007-11) that got a print release, then retold as a separate manga adaptation (under the original author's supervision). These OVAs adapted the web comic, whereas the 2021 anime TV series adapted the second manga. (A manga adaption of a manga? Seems weird, but what the hell.)
They're indistinguishable, though. Same characters, same story, ultimately the same author. I wouldn't have known they were based on different versions of the same story if I hadn't googled it. The art's different, admittedly. I quite like this style. The simpler look feels more iconic, while I approve of the darker hair colours. Both versions of the story are very likeable. If I had to pick out differences...
1. Hori comes across more strongly in the retelling. There are a few story beats where I was thinking Hori hadn't come across as vividly as I'd expected, compared with the later anime. She improves in later episodes, though.
2. Miyamura feels slightly different. His violence and aggression feel more like part of the character, whereas they were more clearly out of place from the TV series's gentler Miyamura. Because of this, the personality shifts/facades in ep.6 don't work as well as they might have.
3. There's a stronger focus on the main romantic storyline. It's all about Hori and Miyamura, with some genuinely interesting scenes where the subtext and motivations are going in completely different directions from the dialogue. The mutual love declaration in ep.3 creates a whole load of awkwardness and anti-logic and "it's only me" idiocy. It's clever and well-written. Mind you, in ep.6 Hori's masochism made me just as uncomfortable as ever. I've decided that I don't mind her being a pervert, but I find it unpleasant to watch Miyamura doing that roleplay she wants. (Note that "a kind person" is one of the show's running undertones, with that poster on Miyamura's bedroom wall that then gets quoted in the last episode's closing credits.)
4. In ep.6, is that family restaurant the one from Wagnaria!! (aka. Working!!)? I love that show. That staff member here looks a lot like Wagnaria!!'s Kyouko, although we never see above her shoulders.
The voice cast are mostly different, but I didn't notice (except for the obvious difference of not having Kenjiro Tsuda playing the teacher Yasuda). Everyone feels right.
It's good stuff. I'd recommend it. Next, the 2021 live-action Japanese TV drama...