There are new features. Here is a list of them:
It has a new eighth day. This eighth day takes place after the seventh day and is different for each path. This new scenario reportedly makes up about 1/4 of the game's content.
It has a fully voiced script of over 20,000 lines.
It now has a Demon Compendium. The Compendium allows you to save an archive of any demon you have. Archived demons can be called back at any time by paying a fee, so you will be able to fuse demons freely without worrying about losing a demon you worked hard on forever. It also contains detailed text on the demons' mythological origins.
There is an new "quick movement" option to make battles go by more quickly.
The graphics are re-done with more detail and a higher resolution.
There is a new Easy mode.
There is a "Survivor's Award" system that's like a combination of an achivement system and the Grade Shop and the Tales Series. Each "achivement" adds a number of points to your total, and these points can be spend on bonuses for your next playthrough.
Has additional demons and skills, as well as multiple save files.
hype hype hype
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Black Turtle did a pretty good job.