You guys ever consider the fact that there are Japanese of Korean and Chinese ancestry ?
The Japanese even has a phrase for ethical Korean Japanese in "Zainichi". Look it up.
There are probably even more ethical Korean and Chinese than you think here. They are of Japanese nationality but racially Chinese and Korean.
It doesn't matter. It's all about now. Most Asians originated from china in one way or another since they all still use their characters in some forms or ways, but that was way before china was unified. It's like referring caucasion or latinas or mixed like tia, rola, maria, or okita, which are more exotic when they're actually from somewhere else. Somehow, in japan and well in America too theyll put you in a racist scenario, which make them vulnerable to be dominated. You can even order a 23&me and get all kind of results. It's rare for someone to be 100% of a certain Asian race anyway. A real Korean city or rural girl is definitely more alarming and exotic than a native one with Korean ancestry even if they can speak some Korean. The title of a Chinese or Korean girl is just more catchy.