Ex characters
In arcade mode level 100 and higher, Ex characters will challenge you. Defeat them to unlock them.
Leopaldon
In arcade mode level 199, defeat Leopaldon to unlock him.
Zako 1, 2, and 3
In GG Boost mode, defeat Kakusei Sol and Ky in the last stage to unlock them.
Kakusei Sol and Kakusei Ky
Play Scramble in RK II Factory under the normal difficulty setting. Finish the last stage with a score of 1,500,000 or greater. Robo Ky II Substance will appear. Defeat him to unlock Kakusei Sol and Kakusei Ky.
Robo-Ky II's Tyrant Rave ver. Beta (Sol's Overdrive)
In Boost or Scramble mode, reach level 1-D. Do not break the container. In the mission, defeat five or more fighters with an Overdrive during the mission (not after). If you have not unlocked any of the Overdrive Chips, you are probably going to hit them with the repeated punching move, or Whatever is Done, A Fellow No Good is No Good. After that, the screen should show the Extra Bonus symbol. This is the time you open the canister. In it, you will find the Warp Bottle. Take it and finish the mission. You will do a bonus mission, then face Robo-Ky II for the first time. Defeat him and you will end up on Zepp, 2-D (the mission where you face the Zaku with the black jeans before taking on the women in black with claws). Do not open the canister here. In this mission, the Extra Bonus is when you knock-out the black Zaku - B before the leader. Then, open the container and you will find the Warp Bottle. Take it and finish the mission. After doing a bonus mission, go to Robo-Ky II. Defeat him and you will end up on the Ninja Training mission near the end of the mission. You will find a container. Open it immediately and take the chip. Then when you go to your Data Bank, equip Tyrant Rave ver. Beta to Lane 6 to have the ability to use Sol's Overdrive.
Antarctica stage
In arcade mode level 100, defeat Leopaldan to unlock the Antarctica stage.