Complete the game on the Normal difficulty and you will unlock New Game+ and Hard Mode. You will retain your party's stats at the end of your first playthrough, but will not keep the Mystic Swords, Aegis Shield, Remote, and all Stethelos components. Your party will start New Game+ as their initial races (not as beast/monster/cyborg/mecha). There are also Free Scenarios exclusive to Hard Mode and New Game+.