If you see squares fonts in the game instead of text, then you are missing windows font called Arial Unicode MS.
    It's a common error in all new mu online clients so make sure to follow the easy steps listed below.

    Why this is caused? Originally mu online game client comes from Korea, and it does not support Latin alphabet.
     

    Fix Guide
    1. Close game client
    2. Download the missing ARIALUNI.TTF font from the link below
    3. Right click on the file you just downloaded and click Install
    4. Alternatively you may download the missing font and copy it to C:/Windows/Fonts or Control Panel > Fonts
    5. Start game client

    https://mega.nz/file/UmNDBSYB#TuMODlWOyzohRw7OGpKW_4-JYIr0as_U-ZQgW1SEdZQ