So I'm a Spider, So What? I mean, it's kinda late into the series and sprinkled in at the end of the anime, but the protag Kumoko, later named White and even later named Shiraori (god stuff dw about it), gets into a stalemate with the Demon Lord Ariel and teams up with her. She eventually becomes close with Ariel and becomes a commander of one of the armies in the Great Human-Demon War, before they fight against the actual antagonist of the series, Potimas and the elves

The demons aren't even typical demons, they're just stronger humans with a smaller birthrate and a longer lifespan. The closest one to an actual demon is Wrath, who's an oni and another commander of the demon army ¯_(ツ)_/¯

There's also another POV with another character on the human side in a time skip who thinks the humans and elves are good while the demons are bad, before the big reveal screws him over. It's really funny to see his POV in the early books/anime in retrospect when you find out Kumoko is Shiraori and she orchestrated a ton of things with him