When I was young (in 1960-80) there was a notion of "(industrially) developed country" and "developing country" (a. k. a. the 3-d world). Japan was the only country in the whole Asia which qualified as "developed". Perhaps this division is out of date. But when you count the number of Nobel prizes you surely count from the beginning, and they are awarded roughly from the beginning of 20-th century. Another consideration is a time lag between the time when the country becomes "developed" and the time when Nobel prizes are awarded to its citizens.
(I do not even mention the time lag between a particular discovery and its recognition, which can be long).
In think this explains the phenomenon that you notice. "Developed country" means good education system and a lot of jobs for educated people, and their high status in the society. Also information infrastructure and other things which help first-class research.
Japan developed extremely fast: less than one generation passed between the
"Meiji revolution" and introduction of science on the highest level. In this respect it is unique. But the discussion of why the Meiji revolution happened, and why it was so successful will lead us too far. You may start with Wikipedia "Meiji revolution". This revolution transformed Japan from
the "3-d world status" to a competitor of Western Europe in less than one generation. Competitor in everything: economy, military might, and science.