Completion bonuses:
By finishing the game you will unlock the Boss battle, Gaara and Kakashi as support characters, and the shuriken pattern.

Refill Stamina/Chakara:
Rotate the Left Analog-stick and/or Right Analog-stick at the loading screen. A Blue Chakara Ball will pop out. Your unfilled Stamina/Chakara Bar will regain about 25%. This can be performed between loading screens with the Konoha symbol in the bottom right corner.