You can customise the touch controls, but only when you're in a dungeon. The settings are not accessible when you're in the Bergsons' house, for example. 

When you're in a dungeon, click on the settings icon (the little cogwheels at the top left of the screen). Then click on ‘Options’ and ‘Controls’. 

Here you can change the location and size of all the buttons to suit you, but make sure they don't overlap! The directional pad can be fixed or floating, and can also be positioned wherever you like on the screen.