Accomplish certain missions to unlock new characters, as well as outfits.

Unlockable	How to unlock
Chris, outfit 1 (Snow)	Clear episode 1-3 in the main game.
Chris, outfit 2 (Ship)	Reach player level 30.
Jessica, outfit 1 (Snow)	Reach player level 10.
Jessica, outfit 2 (Ship)	Clear every stage on Trench difficulty.
Jessica, outfit 3 (Terragrigia)	Reach player level 40.
Jill, outfit 1 (Ship)	Clear episode 1-3 in the main game.
Jill, outfit 2 (Beach)	Reach player level 5.
Keith, outfit 1 (Snow)	Clear episode 4-6 in the main game.
Keith, outfit 2 (HQ)	Clear 50 missions.
Morgan	Find the real exit on stage 21.
Norman	Obtain all rare weapons.
O'Brian	Clear every stage on Abyss difficulty.
Parker, outfit 1 (Ship)	Clear episode 1-3 in the main game.
Parker, outfit 2 (Beach)	Reach player level 20.
Parker, outfit 3 (Terragrigia)	Obtain one rare weapon.
Quint, outfit 1 (Snow)	Clear 100 missions.
Quint, outfit 2 (HQ)	Reach player level 50.
Raymond	Clear every stage on Chasm difficulty.