If you complete the crossover story, you can play from the beginning again and again by going to "New Game+" on the Symphony screen.
There are many sub-events in the towns and other areas, which you can check via the event list button.
You may be able to enjoy new discoveries and branching stories the second time around.
Also, after unlocking "New Game+," you can skip scenes you've already watched.
Take this chance and play through all the events.