crille

Non-ASCII characters can be used in the URL, but they have to be encoded (RFC3986). URL encoding is widely used (e.g. Wikipedia http://ja.wikipedia.org/wiki/Wikipedia:%E9%80%A3%E7%B5%A1%E5%85%88). 
This plugin encodes NON-ASCII characters in the slugs of your pretty permalinks. So your slugs may look like <code>fußball-in-nürnberg</code> or <code>連絡先</code>.

Permalink Encoding

This plugin encodes NON-ASCII characters in pretty permalinks by using Percent-Encoding described in RFC3986.

kr4ft3r

Multisite support added in v0.6!
Notice: this plugin will not have further major updates. If interested in new features, please upgrade into this compatible replacement: https://wit.rs/wp-plugins/wit-custom-output 
After uninstalling the WPCHTMLP and installing WIT Custom Output, your old custom pages will still work, but with better interface, more features and regular updates.
WP Custom HTML Pages plugin has two functionalities:
1 – Create a custom HTML document output at a custom permalink address, completely bypassing WordPress templating. This is useful in cases when you just want to output some HTML without uploading the page to the server.
2 – Create a shortcode which outputs your custom HTML.

WP Custom HTML Page

Display full custom HTML on custom permalink address, or put it inside content as a shortcode.

Permalink Encoding vs WP Custom HTML Page