"WordPress Locale Mechanism"
Please welcome, Seisuke Kuraishi.
I'm Seisuke Kuraishi.
Do you remember, in WordPress 4.0
There are big changes around language functions.
WPLANG variable became deplicated,
and it replaced with Master Value in Language Chooser.
This screen is doing installation of Japanese language
and not connected with external network.
English and Japanese is in "Installed" and Japanese is active.
From this condition, delete Japanese translation file.
Then, the string "Installed" was changed from Japanese to English
and Japanese was disappeared. now there is only English.
"Active" is shown below.
but if we can't get language file because of environment,
we can't set Japanese language.