:/ @ buy....
Get a social from a friend (legal) or use the powers that be from an engine (not so much - therefore I'm not providing further guidance on how to find it), follow a guide on youtube titled Nexon KR 20010 Registration Guide (if you can't read korean, they'll translate the registration page for you).
Turn on the Korean Keyboard layout along with Microsoft IME so you can type the required CAPTCHA.
Here are more details on Korean SN format vs Social Sec in US:
Every Korean resident is assigned a Resident's Registration Number(주민등록번호), which has the form 000000-0000000. The first seven digits have his/her birthday and gender, where the first six digits are in the format YYMMDD.
If you need more help... google it.