Have you ever seen this?

http://cfs1.tistory.com/upload_control/download.blog?fhandle=YmxvZzc2OEBmczEudGlzdG9yeS5jb206L2F0dGFjaC8wLzE1MDAwMDAwMDAwMS5qcGc=
or visit http://www.palgle.com

This banner is showed as only Japanese. why?

They're the AdSense suggest banners, you know.

It's funny...
The pages are in Korean but the ads are in Japanese. LOL.
Too bad I can't read Korean and Google Translator for Korean to English isn't that good, so I can't answer your question.
They ads are really cool. :)