Unlockable Weapons:

To unlock a specific weapon, beat the corresponding storyline.

Heal Cannon
Beat the Full Hero storyline
Omochao Gun
Beat the Semi Hero storyline
Egg Vacum
Beat the Normal storyline
Satellite Laser
Beat the Semi Dark storyline
Samurai Blade
Beat the Full Darkstoryline
Shadow Rifle
Beat every storyline and then beat the last story