Adjacent to the Attack ability is one called Blue Magic. Selecting this will bring up a subscreen with all the Blue Magics you have learned. To get 100% with the Gun Mage DS you need to fill this subscreen with all the necessary spells.

To learn a Blue Magic you must have a fiend use the skill on the girl equipped with the Gun Mage DS. Here is a list of all the Blue Magics

Fire Breath
Seed Cannon
Stone Breath
Absorb
Blaster
White Wind
Mighty Guard
Bad Breath
Heaven's Cataract
Supernova
Cry In The Night
Drill Shot
Mortar
Annihilator
1,000 Needles
Storm Cannon