You cleared game once so now you can go for it again with a bit of bonuses! If you try to load your After Story clear data you will see this screen. If you go for trophies check which trophies you're missing before starting. It will give you a nice idea which things you can ignore. Especially look for battle trophies. They usually don't need additional work, but you still can miss some like use of some moves or kill bonuses if you're good without them. Also, note which bond trophies you're missing and friend notes you haven't filled. There is also two trophies which can be gotten only in NG+: collecting all chests and clearing all dungeons with S. Your data on open chests and dungeon grade will be carried on, but there are 5 additional dungeons available only in NG+, so you will get these two trophies after clearing them.