Tsunade
How to unlock: use Jiariya and beat single player mode.

Asuma Sensei
How to unlock: you must beat the game with Shikamaru, Ino, and Choji. You must also get Jounin with them in Survival Mode.

Garra & Tamari
How to unlock: beat the game with Shikamaru.

Deidara
You must complete Story Mode.

Itachi Uchiha
Description: unlock Itachi Uchiha
How to unlock: Beat Sasuke Uchiha's Story Mode.

Shino
How to unlock: beat the game with Kankro.

Kasime
How to unlock: beat the game with Jariyah.

Unlock 4th Hokage
Defeat the game's story mode on the fourth difficulty.