Then, i should consider switching to Unicode.

Thank you so much for your helpful answer!

You're right!
The Korean data displayed in System Explorer > Globals appears as something like ÃÖºÀ³².

So, let me make sure I understood this correctly.
As I understand it, the data in the Cache database is currently stored using KSC5601/EUC-KR encoding, but the management portal(or another tools) in my local device is trying to interpret it using ISO-8859-1, which is why the characters look like broken.

If that's correct, is there a way to configure the JDBC connection to interpret this data using EUC-KR encoding?

Sorry for the late reply.
When I check the locale from the given path, it shows: 

"Your current locale is: enu8 (English, United States, Latin1 (ISO 8859-1))"

And when I ran the Example code, the retrieved data appeared as "???".

To provide more context about my situation:
The legacy application was originally developed in vb6, and within that program, Korean characters are displayed correctly. There’s probably some encoding configuration set in the application, but since it was compiled into a Dll file, it's difficult to check or verify the details.

However, when I access the data through the Cache Management Portal, Cache Terminal, VSC, or IntelliJ, the Korean text appears broken, as I mentioned earlier.

Sorry for the insufficient answer, as I'm not very familiar with Cache.
When I run below code in the Cache terminal, it returns 0, so it seems to be the 8-bit version.

Write $system.Version.IsUnicode()

And the default locale appears to be set to Latin1. (When I check from the Management Portal, it shows as Latin1. If there's a more accurate way to verify this, please let me know.)