In closing the adventure, you will be able to continue to play after the end sequence and credits, but there will be no monster to fight. Go to the place where you Reala met for the first time near the tower in the forest. Wait until the end of the kinematics and agree to save on a separate file. In charging that party, you will have access to a Grade Shop where you can redeem your points, the New Game + mode to start a new party in order to get the 15 stones scattered around the world to enter the optional dungeon.