hi Yuji.
EMLH is not harmed by any caches.
You'd better to look inside cache/db%3Asystem_rss.html .
You will find the language tags in it.
The other part of languages and tags will be removed the last stage of outputting.
All you have to do is specifying the language manually.
eg) this site:
http://www.peak.ne.jp/xoops/backend.php?easiestml_lang=xlang:enhttp://www.peak.ne.jp/xoops/backend.php?easiestml_lang=xlang:ja