Robot detective "K" belongs to the newly established "Special Investigation Unit" of the Metropolitan Police Department. He is a fighting machine with an expressionless mask, a blue-black steel body, and powerful weapons, but he is more gentle than a human being. He teams up with Shiba, a stubborn old detective who hates mechs and despises "K," and daringly challenges the mysterious organization "R.R.K.K. (BAD)" to solve a number of mysterious cases!