Can Korean nationals return to China after being illegally detained in China?

I can't. Those who illegally stay in China and violate the exit and entry administration law can be detained for up to 15 days. If deported, they are generally not allowed to enter China for several years or for life. Illegal immigration refers to those who enter the country legally, but stay beyond the time limit allowed by the local government, that is, the visa extension is refused, or the visa expires for more than three months, and they lose their legal status and become illegal immigrants.