Don't use your ninja cards. Save them up for when you have Naruto, Sakura, Kakashi/Guy, Kiba, Shino, Tenten, Ino, Shikamaru, Choji, Hinata, Neji, ect. So you can use them to boost up the peoples morales that are Low.
This character who is the leader and teacher of Team 7 becomes unlocked by clearing the game and then going to his house and having a brief conversation with him. When you do this and then select Kakashi he will give you his info card.
When you go to the Ninja School in the main town speak to Konohamaru who is on the ground floor between the 'Mission' and 'Challenges' doors and quickly enter the following codes on the Romanji grid areas to receive an item that when used will unlock the bonus character after the game has been completed.
Unlock Itachi Uchiha: Enter the code G, B, E, I, D, A, L, F.
Unlock Jiraiya: Enter the code E, B, J, D, A, G, F, L.
Unlock Kankuro: Enter the code A, L, J, K, B, E, D, G.
Unlock Kyuubi Naruto: Enter the code G, J, H, L, B, F, D, E.
Unlock Gaara: Enter the code D, K, F, I, A, B, J, L.
Unlock Temari: Enter the code H, F, I, C, L, K, B, G.
Unlock The 3rd Hokage: Enter the code C, G, H, A, J, B, E, L.
Unlock Gai: Enter the code I, K, A, G, D, E, F, L.
Unlock Iruka: Enter the code J, G, D, L, K, A, I, B.
Unlock Orochimaru: Enter the code A, H, F, B, L, E, J, G.
To get this item go to the Ninja School in the main town and speak to Konohamaru and enter the following code (C, F, J, H, I, L, E, G). Then when you have completed the game take the Silver Blade ticket to Shizune and she will give you the 2nd Hokage's Blade.