Aruon is Falcom's (Creator of Ys) Korean distribution company.

Recently they started a new service called FROG that let's you play YS:Origin, YS:The Oath in Felghana, Vantage Master 2, and Eiyuu Densetsu FC for free with limited ads.

Go to http://www.aruon.com/member/join_step_4.php

Accept the agreement then enter the Name and KSSN.

Now follow the steps here

ID(Enter your username here and click the button next to it to check it)
비밀번호 (Password, must be 8 letters/numbers long)
비밀번호 확인 (Confirm password)
비밀번호 퀴즈 (Password recovery question)
비밀번호 퀴즈 (Question answer)
이메일 (E-mail)
주소 (Zip Code/address, see nzrock's FAQ)
연락처(Phone numbers)

Don't check the SMS box!

Leave the next box blank and type anything in the last one.

Click the button at the bottom.