There are four kinds of Ninjutsu in Shinobi for the Nintendo 3DS: Fire, Earth, Water and Lightning. You can select these while playing by tapping the appropriate icon on the 3DS touchscreen, and use them with the L button.
Here’s a brief look at each kind of Ninjutsu with some new screenshots:
Fire: Allows you to cause a large amount of damage across the entire screen:
Earth: Jiro defends automatically for a while, making him near invincible. His movement speed and attack goes up as well, but once the Ninjutsu gauge is depleted, you lose the ability to throw shurikens and your HP goes down to 1.
Lightning: Allows you to negate damage received from enemies up to three times:
Water: Increases Jiro’s jump height and also increases his shuriken recovery rate: