It's a very good game, although a bit buggy. If you follow these three steps, you'll have more fun and less bug problems:

1) Play on Casual mode so you only identify tsukumogami once in regular battles. If you don't, then completing your Spirit Index and level grinding will be painfully slow.

2) Have two save files. The first one is for the Capital only. Do not overwrite this save file anywhere else.
The second one is for in all other areas. Use it often, as you will sometimes encounter an error during battles. I think it is caused by a memory leak. When this happens, quit the game and reload your area save file from before the battle.

3) The skull hunting sidequest is also buggy. Unless you do a lot of level grinding, you may want to leave them for New Game Plus. When you enter a new area, ignore the skulls and unlock all of the map. This includes defeating any optional bosses.
Afterwards, you should overwrite your area save file. Now clear all the skulls in the area without saving and visit Soujun. Hopefully he recognises that you got all the skulls. If he doesn't, then reload your area save file and try again until he does. This issue may also be caused by a memory leak.

Also, once you beat the game for the first time, you unlock some extra features on the title screen such as a minigame with bonus CG rewards.

The DLC visual novels are also really good, so buy the complete collection.