While some Dragon Ball Sparking! ZERO characters are available from the get-go, you can find a handful of characters (not including different variants or forms) throughout your playthrough.
There are multiple ways to unlock characters: buying them in-store, going through the main episodic quests and branching paths, getting your player level up, or using Dragon Balls. With so much on offer, here is every unlockable character and how to get them.