Spent part of the day checking this out.

It's a light novel original. There's a manga adaptation, and that's where I started. It wasn't very good though, and I was pretty sure, as is often the case when a lot of the text in the original is the thoughts inside the protagonist's head, that the manga was just skipping over big chunks of it. I kept plugging away through four chapters (mostly because they were done by Skythewood, and I trust their judgement - our tastes strongly overlap), but then found that 5 and 6 are missing from mangadex, some sort of sniping war has broken out starting with chapter 7, and Skythewood has apparently dropped it.

In sorting all of that out, I discovered that Skythewood has been translating the light novel, so I just read that instead. And discovered that the manga has indeed left out huge chunks of the original.

It's pretty good all in all. It's very definitely of the "oddly proud and determined loner finds himself surrounded by pretty girls" subgenre that seemed to really take off with the success of Oregairu. The twist with this one, and to its credit, is that all of the girls are romantic losers who initially turn to the protagonist for a shoulder to cry on (either figuratively or literally), then it expands from there, as they come to appreciate him more broadly and he starts coming out of his self-imposed exile.

And thankfully the anime art appears to be based on the LN illustrations rather than the manga.

So - IMO, the LN is pretty good, the anime is promising, and the manga can be ignored.