Korean chicks next to Chinese have the flattest asses in Asia.
She either 1) got a buttlift or 2) she does squats. My money is on 1.
On a related subject my theory on why womens breast sizes are actually getting smaller over time equates to Korean women getting uglier. They are literally spending billions on cosmetic surgery to ensure future generations are doomed to repeat living a lie.
Sounds like standard biology about natural or artificial selection and it's influence on human anthropometry