Mixed race -- or half-Korean, half-white.
Aren't Koreans white?
It is colloquial American English. You'll hear it a lot here.
https://www.npr.org/sections/codeswitch/2014/12/15/370416571/half-asian-half-white-no-hapa
keannu—I assume (possibly wrongly) that you want to make a statement about culture/heritage rather than race.
It may be that the distinction between these two things is not clear.
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