Neocities.org
Hey, just so you know, you can upload custom font files to use in your website. That way, users won't have to manually install Mona Font. Check this out: https://www.w3schools.com/css/css3_fonts.asp In case you're worried about licensing/etc.: I don't know a lick of Japanese, but running Mona Font's readme through an online translator, it seems the font is in the public domain. Cool site, by the way. :)
I just realized that you've got a font included with your Femto.css framework, so you already know about this. Sorry for telling you what you already know. Though maybe you don't know this: Font files, including TTF files like Mona Font, are allowed to be uploaded by non-supporter accounts: https://neocities.org/site_files/allowed_types :)
Thanks for the info! I'll upload the ttf file :D
update: sorry, i couldn't add the font. The ttf file slows down the page loading speed way too much. I also tried converting the file to woff using a npm script, but it didn't worked. Looks like Mona font is just too old to be .woff. Sorry! :c