LADIES AND GENTLEMEN THIS THREAD IS LIKE VOLDEMORT, IT CANNOT BE NAMED

In short, the Word otaku have a Heavy meaning depending on where you use it, in Japan it means exactly what Malthe says, but in the other part of the world it can probably mean what Razmos says.

It's pretty much this.

Being an otaku in Japan is generally negative because it means being overly obsessive while in western countries (due to the word being butchered, pretty much), it basically means being an anime fan.

While it depends on where you use it, I'd go with the origin of the meaning and say that this guy IS that kind of otaku.