By accomplishing a variety of tasks, you can unlock new characters to use in the game. Zako A, B, and C can only be used in Vs., Training, and Boost modes; Leopaldon may only be used in Vs. and Training modes.
First of all, you have to have Ky and So\'s Ex versions unlocked. Play Robo Ky II's Boost Mode on Normal difficulty, and beat Stage 5-E (Last Dance) with 1,500,000 points or more, and a giant Robo Ky II will appear. (Robo Ky II: Substance.) Defeat him to unlock Kakusei Ky and Kakusei Sol. Select them by highlighting Ky or Sol on the character select screen, and press Start twice.