What is “otaku”? Otaku is a Japanese term for people with obsessive interests, commonly the anime and manga fandom. The modern slang form, fans used it past the point in their relationships where others would have moved on to a less formal style. In modern Japanese slang, the term otaku is mostly equivalent to “geek” or “nerd”, but in a more derogatory manner than used in the West. However, it can relate to any fan of any particular theme, topic, hobby or form of entertainment.