I would highly suggest doing the Unison dungeon on the first play. The second play all enemies get twice the health and 1.5x attack and defense, so you will need your characters all at level 99. It can be done at 75ish on the first play. Saves a ton of time.
Your character levels do not transfer to the second play.
~Alan | Anime
I award you no points, and may God have mercy on your soul.