I actually found Japanese fanfic once (and was too lazy to read through it, I should, would be good for my abysmal Japanese skills). Do you have any links (and no, I'm totally not asking because I once thought I might want to write my thesis about Japanese fanwork culture)?

And the way I understood it, fanfic is just called doujinshi as well, or am I confusing something?

I also think that the language barrier between German and English isn't as high as the one between English/German and Japanese. I know I think Japanese is way more complicated than English, mainly because English is kind of like the dialect spoken where I grew up. But on the other hand, there are very few German source materials that people write English fic for. I linked to the Eskimo Kiss Project in reply to one of sabeth's posts, which is basically the fansubbing of a German soap, and that's a really rare thing to happen in English fandom.