The demo for RGG 5 was released on the Japanese Playstion Store on Monday December 26th 2012. It includes parts of Kiryu's story in Part 1 Chapter 1 and a couple of substories. Only selected parts of Nagasu are open to players to explore.
This link used to forward you to a 30 minute Youtube video of KHHsubs translation of the cut scenes and the text of the sub stories that appear in the demo, but it has since been removed by SEGA. [17/12/2012].