After defeating the last boss and watching the final cutscene, you will be offered a chance to enter into a New Game+ mode. You'll unlock a new costume for your character, which replaces the original one, and all of your items and past upgrades to units will be converted into RUVE for your next playthrough.

Unlockable	How to unlock
Alternate Costume	Begin a New Game+.
New Game+	Finish the game.