1. Your clientinfo.xml config should have next:
<servicetype>korea</servicetype>
<langtype>0</langtype>
2. Now, you need to configure MySQL server (or MariaDB, or whatever you have)
Options what is interesting for you is next:
[client]
default-character-set = utf8mb4
[mysql]
default-character-set = utf8mb4
[mysqld]
character_set_server=utf8mb4
collation_server=utf8mb4_unicode_ci
3. Now, create a new database after applying these settings.
Will be created a database, with correct encoding (as far as I remember utf8mb4 support Korean characters pretty well).
4. Now, import your SQL files there, like you always do. (main.sql, logs.sql, etc)
5. Now, open your inter_athena.conf and find next option and make them hardcoded info what charset to use:
// You can specify the codepage to use in your MySQL tables here.
// (Note that this feature requires MySQL 4.1+)
default_codepage: utf8mb4
At this point everything will be okay, but depends on a lot of differences between a lot of charsets default in different regional operation system with national languages, charsets of the windows can be different, 1252, 1251, etc.
6. You can manually force a client to use utf8
For that, you need to download dininput.dll & ini file: DOWNLOAD DININPUT or ALTERNATIVE LINK if the previous one will die.
7. And now run your client and play. Everything should be good.