Non-English characters show jumbled up

While editing Japanese or Chinese characters, with the permalink structure of /%category%/%postname% for example, the permalink shows up in hexadecimal (encoded?) equivalents of the respective characters.

Screenshot:
https://i.imgur.com/slgR0.png

Is there a cure for this? How can I make sure that the characters appear as usual?

I have the following in the wp_config.php, but this doesn’t help:

define('DB_CHARSET', 'utf8');
mb_internal_encoding("UTF-8");
mb_regex_encoding("UTF-8");