The fake far right movement in Japan run by Koreans pretending to be Japanese. Probably at least partially funded by the Korean government (north or south). Affiliated with the yakuza (also controlled by Korean "zainichi").
Like neoconservative Jews in America, the uyoku dantai Koreans' goal is to undermine the traditional right wing in Japan and make it look a stupid caricature to mainstream Japanese, while at the same time making it serve their own purposes (weakening Japan with immigration, crime, etc.).
uyoku dantai yelling in the street: "My name is Kim Chon I mean Satoshi Nakamoto! Long live the Emperor! Tenno Banzai! Annyeonghaseyo!"
Koreans living in Japan pretending to be Japanese. May or may not have been born in Japan. To the westerner's eye they appear no different from real Japanese.
Despite claiming to be "Japanese," zainichi have enormous Korean pride (like all Koreans) and will usually boast to you within a few minutes of first meeting that they are in fact Korean. They also use their Korean name whenever possible. In reality, they are no more "Japanese" than a Swede or Ethiopian who happens to be born in Japan.
They are infamous for running the mass media in Japan, the fake far right movement ("uyoku dantai") as well as controlling the yakuza criminal underworld (gambling, prostitution, drugs, etc.). Most "bad neighborhoods" in Tokyo and Osaka are actually zainichi neighborhoods.
American in Japan: "Hi! My name's John. I'm here studying the Japanese language. Nice to meet you."
Zainichi: "Hi John. I'm Korean. What are your hobbies? I'm Korean."