It's weird, it's a slice of life anime where the main character thinks he's a superhero or something, but when he figures out he really isn't at all near the end of the series, he loses his mind between episodes and the last like 1/3rd of the show is him in his fantasy world in his mind going on over-the-top superhero adventures with his friends who are also now superheroes. I don't remember the name of the show or any of the characters, but it was on Netflix for a while a few years back and that's how I first saw it, but now I can't find it.

The nearest I can think of to that description would be Samurai Flamenco.