Kuro was once a housecat who cannot defend himself from dangers like burglars who Kuro had horrible temper, and gets angry and out of control easily, but he is noble and good-hearted He loved elderly couple who adopted him dearly, 

Kuro was originally a domestic cat with black fur and white underbelly, but after cybernetically modified by Dr. Go against his consent, he now gained extremely durable armored skin and various armaments includes a portable weapon storage within his body. 