My case and point? ....

Flat on both sides

And yes, this one IS a woman.

My 'work' associate, also flat behind.

You can sorta see her rear end is rather 'tame'.

Dancers are out event, of the dance group Splendor - also very flat in the rear.

A half-breed, her father is from Canada, her mom's Japanese. She developed a bit of a bump at the back.

Japanese and flat

NOT Japanese and NOT flat

NOT Japanese and NOT flat (starting to see the difference here, ppl?)

Oh, and here's a special one just for that user tetsurousou... maybe the next one too.
So... c'mon... challenge me... tell me I don't know what I'm talking about and only stereotyping as many of you little troll-hogs like to do. Hit me with whatever you've got. Tell me how the Japanese women in YOUR country... or perhaps the women you think are Japanese, who have lived there for multiple generations, have rounded rear-ends. C'mon, give me whatever you've got.
GOD DAMN I LOVE BEING RIGHT!