"Black belts are experts in unarmed combat. They can boost their attack power to deal massive damage, but be careful not to boost too much!"
The Black Belt(空手家,Karateka?), also known as Karateka or Master, is a Job class in Final Fantasy III. It is gained from the Water Crystal in the NES version of the game, while it is gained from the Earth Crystal in the DS and iOS versions. Black Belts are masters of combat, able to use only their fists for massive damage. They are capable of linking their mind and body to store energy for an upcoming strike. Black Belt is considered to be a powered up version of the Monk job and one of the most powerful jobs in the game. Raising the Job Level of a Black Belt will raise his/her bare handed attack by 2.
Storing up energy, the Black Belt will be able to do more damage, with the damage increasing even more if they are bare-handed. Using the command twice boosts the attack even more, but using it three times will hurt the Black Belt and release all the built-up energy.
Just like the NES version, Boost will increase the Black Belt's power. The first use will double the next attack, a second use causes the damage to triple. However, if Boost is used 3 times in succession, it overloads, cancelling the charge and cutting the Black Belt's current HP in half.
Under the right circumstances, it is possible for a Black Belt to defeat Cloud of Darkness in a single hit.