Some players see squares in the game instead of text. That means they are missing windows font called Arial Unicode MS.
It's a common error for all new MU Online clients, so make sure to follow the easy steps listed below:
1. Close the game.
2. Open the game client ("Escape MU Season 15" folder).
3. Open the "Fonts" folder.
4. Right click with your mouse on the file "ARIALUNI" and click Install.
5. Start the game.