Genshiken is 10/10 manga/ani yet it declines as it progress. The first part with original crew is the best and it get worser as the Fu-joshi takes over the story. It's still good, but at that point I only read it for Madarame.
Yet, genshinken focus more of otaku culture rather than "succubus saves boy"
Denki-gai_no_Honya-san is another otaku anime i like. But it's not dark at all. 9/10
Kuragehime - Fu-joshi shit, it was decent. 6-7/10
WataMote: can't remember opinon about it, ok i guess
for real, try Yojouhan Shinwa Taikei 10/10
Might not be what you looking for but there's nothing as nhk in ani world. maybe manga idk