Kotarou

Kotarou is one of the main characters in the series. A boy genius dressed in a black catsuit who helps Dr. Go and Mi-kun out by assisting in their inventions or building his own. He has an obsession over Kuro-chan, and tries to prove to be as powerful as him. This idea of his was the result of being an outcast. He is experienced in technology, with an IQ of 200.

Even though a remarkable genius, Kotarou's lack of common sense is his common flaw. Before meeting Kuro, he was an avid retro gamer with his own intelligence to conceal his loneliness. Though very earnest towards making new friends such as Dunk and later Kuro and the gang, his naiveness for approaching strangers can often land him in trouble.

Kotaro's self-made his black cat costume based on Kuro-chan, but unlike Kuro's normal skin costume, it was outfitted with bulletproof and insulative features as much as to withstand high voltage.