Characters in Naruto Shippuden: Ultimate Ninja Storm Revolution are unlocked by earning the in-game currency known as Ryo. Do note that there is no shop to buy these characters as these are automatically unlocked after reaching a certain milestone.
By an educated guess, it roughly takes around 1.7 million Ryo to unlock every character in the game across all game modes. You can go with Ninja World Tournament and Ninja Escapades to start earning Ryo.
Players with Naruto Storm 3 Full Burst game save files on their systems will let them receive some amount of Ryo right off the bat.
However, like I’ve mentioned above, going with this way will take quite a long time to unlock each character. Therefore, we’ve discovered a couple of ways using which you’ll be able to earn tons of Ryo in a matter of hours.