The definition of Japanese people - Homogeneous nature of Japanese society

On the previous article, I wrote "3 Japanese won the Nobel Prize in Physics".
Yes, 3 JAPANESE. All news in Japan also say so.

But one of them, emeritus professor at Chicago University Yoichiro Nanbu lives in the US now and got American citizenship when he was around 50 years old. So American media say about three Nobel laureates in physics "one American and two Japanese".

I can understand that they say so. Chinese American, Italian American, Indian American, Japanese American etc... various races gather in the US, and they are Americans. But for Japanese people, professor Nanbu is surely Japanese.

Probably "blood" is more important than nationality on a piece of paper which means laws or something in administration, for Japanese people. For example, a figure skater Rena Inoue. She moved to the US to improve her skating and became a US citizen in 2005. (More info about her is here.) She now participates in competitions as an American skater with her partner who is an American guy. But most Japanese regard her as Japanese.

On the other hand...
Many non-Japanese athletes came to Japan and plays in Japan. Some of them obtained Japanese citizenship. But for Japanese people, they are "foreigners".

When people ask someone about his/her country of origin, they say "Where are you from?" in English. But what Japanese truly want to ask is probably "Where is your blood come from?"