In English, an otaku (plural usually otaku, since Japanese words are not pluralized using an "s") is a variety of geek (or an overly obsessed fanboy / fangirl) specializing in anime and manga. (From Wikipedia, the free encyclopedia)
Otaku is no longer mere Japanese subculture.
Takashi Murakami inserted Otaku culture such as anime and manga into the context of contemporary art and he had a success in the United States.
In Venezia Biennale 2004 (the international architecture exhibition), Japanese pavilion showed the space produced by Otaku culture in city.
It seems to me that people in the world see Otaku culture as the originality of Japanese culture, or Japanese ourselves introduce it as our originality.
Anyway, Otaku got popularity not only in Japan, but also in the world.