My experience with the Japanese is that they are courteous and polite to a fault; unless you’re at war with them. Then their manners go right out the window.
Yes they were vicious in WWII. I know some older folks who served in the Pacific Theatre who would never be able to say a kind word about the Japanese, or even a single Japanese.
My experience is limited to my daughter’s experience there, and it was just amazing. The day she left her little village, literally half the population came out to the train station to see her off .. with gifts, tears, etc. And that train was at the crack of dawn! Hell, I wouldn’t get up to see my daughter off at the crack of dawn .. I’d tell her to call a cab and let me know when she arrived where she was going ;)