I noticed this a lot while I lived in Japan.
The Japanese are a mixed bunch. The Ainu/Jomon (Caucasians) were in Japan quite a while before the asians migrated into the area.
I had a Chinese employee (from Hong Kong) who went for a beer with me once, after one beer, I had to physically help him out of the bar and drive him home, no kidding. That's where the Native Americans/American Indans get the 'alcohol thing' from, north China. BTW, there were no American Indians (as we know them today) in North America prior to 6,000 years ago. Prior to that, they were all the Kennewick Man variety, Ainu/Jomon, Caucasian 'like.'
The Japanese, who handle alcohol better than most Asians, are a mix of the Chinese/Ainu/Joman stock.