Nikkes are manufactured with Code Chip sets in them or their weapons. With the correct chip set, they can deal bonus damage against enemies with certain elemental type or vice versa. The code names are abbreviations based on the Greek mythological deities.
Code H.S.T.A. (Fire)[]

Nikkes with this chip set deal additional 10% damage against wind-type enemies. The code name is based on Hestia, the goddess of the hearth.
Code P.S.I.D. (Water)[]

Nikkes with this chip set deal additional 10% damage against fire-type enemies. The code name is based on Poseidon, the god of the sea.
Code Z.E.U.S. (Electric)[]

Nikkes with this chip set deal additional 10% damage against water-type enemies. The code name is based on Zeus, the god of thunder.
Code D.M.T.R. (Iron)[]

Nikkes with this chip set deal additional 10% damage against electric-type enemies. The code name is based on Demeter, the goddess of the harvest and agriculture.
Code A.N.M.I. (Wind)[]

Nikkes with this chip set deal additional 10% damage against iron-type enemies. The code name is based on Anemoi, the wind gods.