Unlock each character by beating the respectable story mode. the level 1 stories are unlocked on a progression. Nuri unlocks Azer's mode Hana unlocks Cecilia's mode and so forth. Kaz's level 1 unlocks after beating all the original 7 character's modes.

Unlockable	How to Unlock
Arin	Clear Arin's Level 1 story mode
Azer	Clear Azer's Level 1 story mode
Brie/Cadie	Clear Arin's Level 2 story mode
Cecilia	Clear Cecilia's Level 1 story mode
Cien	Clear Cieni's Level 2 story mode
Dark Titan	Clear Kooh's Level 2 story mode
Kaz	Clear Kaz's Level 1 story mode
Kooh	Clear Kooh's Level 1 story mode
Lola	Clear Azer's Level 2 story mode
Max	Clear Max's Level 1 story mode
Minti	Clear Kaz's Level 2 story mode
Pipin	Clear Nuri's Level 2 story mode
Quma	Clear Hana's Level 2 story mode
Tiki	Clear Max's Level 2 story mode
Titanboo	Clear Cecilia's Level 2 story mode