To change your font, you must first complete the Custom Patching Tutorial and enable TrueType Fonts.
Tutorial - Custom Patches
Without this, the game won't read your new font.
Find your MabiPro directory where you installed the game.
You will need to create the following folders if they don't exist.
Find your favorite font file, in .ttf format, and copy it into this folder.
Right click and rename it to "japanese.ttf" without the quotes.
(If you don't have file extensions turned on, just call it "japanese" instead.)
If you aren't sure where to find a font like this, check C:/Windows/Fonts or websites like http://dafont.com
Launch the client and test it out! If done right, your font will appear ingame.
We hope you enjoy your time on MabiPro!!!