You'll need a 16 gigabyte USB memory card to play Dragon Quest X. While you could use any old memory card, Dragon Quest fanatics may want to pick up this officially licensed accessory from Hori:
The Dragon Quest X USB Memory 16GB accessory will be released on August 2, priced ¥2,362. In addition to the DQ markings, the device has an LED which lights up when it's being written.
Buyers will get a code for a special t-shirt for use in DQX.