The fonts (developed by Roman Czyborra a very long time ago (1998!) and documented here) are defined in the file unifont.wff on the SD card. Before a character is displayed, its 32-byte definition is loaded from the file, starting from the calculated address.
The simple sketch used in the above video can be found here. It was tested with Arduino 1.0.4 and does not require the EReader library (but requires the unifont.wff file on the SD card).
PS For the non-Chinese speakers/readers, the displayed symbol is "nihao" ("hello"), Unicode 0x6829.