Well, I've never seen the anime, but from the way you describe it, it seems to be quite botched. Sounds as if they included the main plot point but skipped all the explanations and the character motivations. I mean, it's not like the original light novel is that good. The writing is pretty amateurish, and the story is kind of garbagey (in a good sense). I mean, the author literally used "chuuni lover" as a pseudonym when he posted the original WN, so what else would you expect. Still, the pacing is extremely good, and, unlike many light novels which lose any sense of direction after a few volumes, the story in this one actually feels like it knows where it is going, and the humor is indeed genuinely funny. The MC isn't a self-insert, and even if he is an edgelord, it kind of makes sense for him to be one after everything he went though, and he's also extremely entertaining to watch.
Also, the relationship between the MC and Yue in the first volume is actually one of the best things about the LN, and it's a shame that it was kind of ruined after it turned into harem. Though on their own Shea and Shizuku are also pretty good.
PS. I've actually just started reading the prequel recently, and I feel like the writing in that one really improved. It's a bit hard to read, honestly, since I already know how it ends.