This is unlocked in the regular mode, either Japanese or English is fine, but NOT Caravan or High Score.
I completed this game only using the same 3 characters the entire time. If you use them and their specific move you'll likely have less trouble, but I can't promise you'll win.
(Moves taken from the Wiki)
Robert Garcia - Hien Senpuu Kyaku (Flying Swallow Whirlwind Leg) - →↘↓↙← + B
(This is a spinning triple kick and you can spam it if you get the timing down right after finishing a kick.) Robert's attacks will likely keep them in the corner and guarding, but they take minor damage while guarding so just keep spamming it.
Benimaru Nikaido - Voltage Fist ↓↘→ - + Y Near Opponent
(Somewhat of an electrified uppercut, you have to be in the enemies face though)
For the third character use whoever I never had to use them, but I picked Cheng due to a solutions recommendation, and would have just spammed the Y button.