This is an awesome feature that allows you to customize your fighting style.  When in the shop tap on Ninjutsu, here you can preview all the fighting moves and how to recreate the moves during a fight.  The arrows represent the direction you need to swipe in order to do each move.  
You also have the option to change the direction of the swipe for each move.  Highlight the move you’d like to customize and decide which direction best fits the move.  Tap on the arrow box on the left side of the screen.  
Now try it in a fight!