This game is what JRPGs should be.
The background of the game is just as Sherrin has said. What they haven't told you is how atmospheric the game is and how it draws you in. The environments blend together extremely well and with the unique graphical style help create a world you will find very attractive and very believable.
The large number of demons help populate this world and adds an exotic flavour which will keep you coming back to this game. Taken from many mythological sources, these demons are visually appealing (well, most of them) and make the game what it is.
The game features quite a lot of customisability compared to most jrpgs. No, you can't change your main character's face or gender, but you can adjust all his stats and skills and make pretty much all the decisions for him. You really start feeling like ‘this is my character, these are my demons’ when you're into the game and you get to choose how it all ends.
The writing is also good, with most demons given a personality that feels believable and appropriate. Soundtrack is very appropriate, with a mix of rock and organ music it really gets you into that mood of a post-apocalyptic world.
The game does have a steep difficulty at times. You will find yourself grinding now and then, but it will not be enough to keep you away. The game will suck you in until you finish it, and then you will start a new game just to beat those old bosses again!