Use any character of your choosing and defeat their shadow counterpart.

Unlockable	How to Unlock
EX Anji-Mito	Reach Survival Level 60 and Defeat Shadow Anji-Mito
EX Chipp-Zanuff	Reach Survival Level 40 and Defeat Shadow Chipp-Zanuff
EX Millia-Rage	Reach Survival Level 80 and Defeat Shadow Millia-Rage
EX Potemkin	Reach Survival Level 20 and Defeat Shadow Potemkin