well being an otaku is not something that most people are pround to be in Japan.
"otaku" (おたく) means "自分の狭い嗜好(しこう)的趣味の世界に閉じこもり、世間とはつき合いたがらない（暗い感じの）者 。" it's kind of the official definition and it says that an otaku is a person that confines themself and doesn't want to talk to anyone (well it's not that positive)
Of course it's just a stereotype toward otaku in Japan, not every fan of manga/anime is like that in Japan.
I hope my explanation wasn't complicated! (If you search the translation of おたく in english it's literally says "nerd")
Oh so its basically just like how people view nerds and geeks in the west.
Am I the only one who doesnt understand why so many manga have female otakus trying to hide the fact that they are otakus? Is it such a bad thing in japan?