I just downlo....BOUGHT this game today and so far it's pretty interesting.
They transfered a bunch of the same backgrounds as the first one but added a little to each one and have created a bunch of new ones as well.
I am really liking the new fighting style. It's almost the same as the first one but tweeked a little to make it even better.
The button combos for the jutsus are the same as well. I really like the new action scenes for the ultimate jutsu moves!! Some have been saved from the previous game but made a bit better.
Currently I see the following as the secret characters: Sasuke, Orochimaru, Kabuto, Itachi and I believe the others are the sound 4. Can't really make them out ^ _ ^ ;;
A sort of rpg section has been added as well. It's called The Mugenio. So far from what I can see you play as Naruto along with up to 3 other characters on your team and are going through this giant castle that was summoned by Orochimaru, Kabuto and probably the Sound 4. Can't really tell because they used the back dashing shadow animation for the other ninjas lol.