Most of them have likely provided KYC to several Korean exchanges easily found by seeing who accepts KRW. Check their wallets for transactions to the exchanges.

If there is a criminal or civil investogation, your korean lawyer can obtain KYC information.

I live in Korea and am registered to a Korean exchange. For the past 2 years all Korean exchanges have required real name ID and a verified matching Korean bank account. Think of it as super tight KYC.

The prosecutors could easily obtain the information you are looking for if your case is accepted. Online pseduonyms get sued all the time here.

Also be careful as defamation laws are extremely strict in korea (read up on it, truth doesn't matter).

Do not make public or republish any info the people in these comments provide.