Kappa

oChief calls himself a Kappa.

A Kappa is a Japanese Mythical Creature. Kappas are said to be based on the Japanese Giant Salamander and Turtles.

The Myth is used to scare children away from lurking near or in rivers or lakes. Since Kappas are said to lure people into the water and pull them under.

During Episode one, Nino says to Kou "He's a Kappa as much as I'm a Venusian".