Earn an "A" rank in Mercenaries mode with the indicated character to unlock the corresponding costume.

Costume	How to unlock
Pirate Leon	Earn an "A" rank as Leon.
Puffy Jacket Jake	Earn an "A" rank as Jake.
R.P.D. Helena	Earn an "A" rank as Helena.
Racer Piers	Earn an "A" rank as Piers.
Samurai Chris	Earn an "A" rank as Chris.
School Girl Sherry	Earn an "A" rank as Sherry.
White Dress Ada	Earn an "A" rank as Ada.