Unlock Asuka
Beat Story Mode with any default Takara character (Licca, Takao/Tyson Granger, Optimus Prime, Microman).

Unlock Bimbougami
Clear Story Mode with all Hudson characters (Bomberman, Momotarou, Master Higgins/Takahashi, Yugo, Manjimaru).

Unlock Manjimaru
Beat Story Mode with any Hudson character (Bomberman, Momotarou, Master Higgins/Takahashi, Yugo).

Unlock Megatron
Clear Story Mode with all Takara characters (Licca, Takao/Tyson Granger, Optimus Prime, Microman, Asuka).

Unlock Moai
Cleat Story Mode with all Konami characters (Power Pro-Kun, Simon Belmont, Twinbee, Solid Snake).

Unlock New Stages
Unlock the Artificial Sun stage by clearing Story Mode with Moai (from Gradius)
Unlock the Oil Rig stage by clearing Story Mode with Solid Snake (from Metal Gear)
Unlock the Tree House stage by clearing Story Mode with Megatron
Unlock the Devil Orchid stage (Manjimaru) by clearing Story Mode with Manjimaru
Unlock the Floating Continent stage by clearing Story Mode with Bimbougami

Unlock Solid Snake
Beat Story Mode with any default Konami character (Power Pro-Kun, Simon Belmont, Twinbee).