This is one of the things that comes up time to time. Now, here we go again.
Today’s news found here and here[in Korean] are saying some Korean professor called 홍윤기 claims Amaterasu was a Korean(Silla) and Sugawara no Michizane was a Korean(Silla) too.
Many Japanese already pointed a whole bunch of mistakes in his claim. And their conclusion was the professor couldn’t even read the documents in old Chinese characters because there are so many pain simple mistakes.
Besides, even I know Amaterasu is a mythical god. Not even a human. Don’t confuse history and myth OK? The Korean myth “Dangun” is considered to be historical fact in Korea and this myth is the basis of the 5000 Years of Korean History™. Japanese don’t confuse history with myth(except some were exaggerated and distorted during the war). Japanese don’t confuse politics with history.
The Korean professor turned out to be a professor at “University of Foreign Language/Studies ” He is not even a historian.
This kind of things make many Japanese making fun of Koreans. I already heard a few Koreans claimed Daisuke Matsuzaka is a Korean descendant (for example, here in English) . (Here is the list [in Japanese] of Japanese said to be Korean-Japanese by Koreans but they are not) This kind of things “he is great, he must be Korean” type thinking are so common in Korean society that there is an article about this in the Wikipedia [in Japanese]. Some Japanese created, just for fun, the certificate of being recognized as a Korean(descendant) by Koreans.
[related post]
A Japanese on Korea 
I wonder why Cho Seun Hui or Joji Obara are totally shunned by those hypocritical –censored–. Oh, right…I forgot, whenever an overseas Korean commits a crime, then suddenly they are not Korean. –censored– hypocrites.