I'll just put this in a spoiler bubble because we're often not supposed to comment about the translation, but I feel like it's very necessary here as it's a big deal. There are issues with the translation, the novel would probably be a fair bit better with a decent translator. He's translating a translated version (japanese->chinese->english) and while it flows decently (but things are undoubtedly lost in translation if you do something like that as just translating it once will screw things up, so every time you do it, errors increase), the grammar is truly bad with errors almost every single sentence and bad choices of words everywhere. I do appreciate the work, but sometimes a translaor should perhaps not translate things if they can't make a decent job out of it because it ruins novels all too often which results in them being, often, permanently unpopular. The saving grace is that these errors are usually not that big of a deal, it's things that are easily mentally fixable while reading, but this also leaves even more doubts about the translation because of the lacking grammar.

Ah, since I have a spoiler bubble up anyway, I'll just mention something since some people post misleading reviews. The MC isn't a scum at all (well, he kinda seems a bit scummy as he seems to become lazy), the whole "there wasn't even any betrayal" isn't really true, they did betray his feelings in quite a few ways and looked down on him. It's also explained that humans here are total tr*sh and the part of the MC accepting the world and siding with the demon king was that he sold half of the human world back to the humans and left so that they, as extreme tr*sh that relies on other people and indulges in stuff, can learn to stand on their own legs. Even if he gave it his all, they wouldn't even have survived because the demon king could easily invade all of them if she wanted to while holding the hero down, her forces are immeasurably much stronger than the humans' forces. The demon king is also a decent and kind one and genocide or even killing a lot of people was never part of the plan.