1. Go to http://nttgame.com
2. Log into the account you wish to set/reset seal code on.
3. Visit the following link: http://www.nttgame.com/en/account/LoginCheck/5 (Or hit my account -> overview -> game services -> security key)
4. Fill the information it requires there, hit "Submit" and you'll receive a mail to your registered email address.
5. Open the mail you received, there you should see a URL.. click on it and it will redirect you to NTTGame's site and ask for a new security code(seal code), just set it and that should do the trick.
Good luck .
How to proceed if the registered email (mine yahoo) was deleted ? Any method ?
I was sent ticket in this issue, however didnt saw any positive response from NTT.