To unlock the character classes below, fulfill the corresponding requirement. 

Archer        - Level 15 Fighter & Healer 
Berserker     - Level 40 Heavy Knight & Monster Tamer 
Cheerleader   - Level 25 Geo Master & Healer 
Geo Master    - Level 20 Fist Fighter & Healer 
Gunner        - Level 15 Mage & Thief 
Heavy Knight  - Level 15 Fighter & Fist Fighter 
Magic Knight  - Level 25 Fighter & Mage 
Majin         - Defeat the second fighting tutorial 
Masked Hero   - Level 45 Gunner & Thief 
Monster Tamer - Level 15 Fighter & Fist Fighter 
Ninja         - Level 30 Mage & Monk 
Samurai       - Level 35 Archer & Fighter 
Shaman        - Level 25 Geo Master & Mage