The fighting modes are seperate. Plays like a traditional fighter, ala Tekken/VF.
The freeroam+platforming mode is amazing though. They really did a good job on making a believeable ninja village. Everything looks like it belongs in it's proper place. I spent 1 hour just walking around town, looking at everything.

Replay-wise, there isn't much. You can finish the whole game in 8 hours, 12 maybe if you want to get all the silly collectibles and finish all the sidequests.
Multiplayer, you can fight online. That's it.
This game is a rental or 2nd hand buy at the least. Still a nice game.