Besides Wi-Fi and Passwords, there are certain ways to unlock characters' ninja info cards.
Some Characters you unlock By Either Winning matches,Getting wi-fi points,or by getting Regional cards
When entering the school, talk to Konohamaru. He is on the ground floor between the Mission and Challenges doors.Entering the password gives you a character item. These character items unlock the character, but it can only be used after you have beaten the game.
Clear the game, then go to Kakashi's house. After a short conversation, select Guy and he will give you his info card.
Go to the Ninja School in the main town. Talk to Konohamaru. After completing the game, take the ticket to Shizune. She will give you the 2nd Hokage's Blade.