Konohamuru's codes - Go to the Ninja School in the main town. Talk to Konohamaru on the ground floor between the Mission and Challenges doors. You will see some Japanese text in the following grid configuration:

[A] [B] [C] [D]
[E] [F] [G] [H]
[I] [J] [K] [L]

Quickly tap the following indicated Romanji grid areas to unlock the corresponding bonus. Note: After entering a character code, you will receive an item that when used will unlock the bonus character after the game has been completed. After entering the "Silver Blade Ticket" code, successfully complete the game, then take the Silver Blade Ticket to Shizune, and she will give you the second Hokage's Blade.

"An Extreme Battle!" mission: H, L, B, A, K, G, C, D
Garra: D, K, F, I, A, B, J, L
Gai: I, K, A, G, D, E, F, L
Iruka: J, G, D, L, K, A, I, B
Itachi Uchiha: G, B, E, I, D, A, L, F
Jiraiya: E, B, J, D, A, G, F, L
Kankuro: A, L, J, K, B, E, D, G
Kyuubi Naruto: G, J, H, L, B, F, D, E
Orochimaru: A, H, F, B, L, E, J, G
Silver Blade Ticket: C, F, J, H, I, L, E, G
Temari: H, F, I, C, L, K, B, G
"The Legendary Haze Ninja!" mission: F, G, E, H, I, D, A, L
"The Legendary Sannin!" mission: B, C, E, G, K, F, H, L
The Third Hokage: C, G, H, A, J, B, E, L

Additionally, the Japanese version of the game has the following code:

Kisame: K, A, G, B, H, L, F, D

Bonus characters - Successfully complete one of the following tasks to unlock the corresponding character:

Enma: Get 20 Regional Cards in Wi-Fi mode.
Haku: Get 10 Regional Cards in Wi-Fi mode.
Itachi: Successfully complete "The Last Of The Uchiha Clan" in Ibiki's mission.
Jiraiya: Play 10 rounds in Wi-Fi mode.
Kisame: Successfully complete "The Messenger From Dawn" in Ibiki's mission.
Nine-Tailed Naruto: Get 100 Wi-Fi points.
Sasuke Second-State: Get 30 Regional Cards in Wi-Fi mode.
Sasuke: Win a Wi-Fi match, then talk to the person next to Anko.
Tsunade: Play 20 rounds in Wi-Fi mode.
Zabuza: Win 100 matches in Special Survival in Ibiki's mission.