Kuro is a housecat for an old couple who cannot defend themselves and are in frequent danger. They rely on him to keep burglars from invading their house, at which he is skilled. Despite his courage, he is in love with the neighborhood dog, Pooly, and he sets out to confess this one day. While heading to see her, he and Pooly are ambushed and injured. Kuro is then kidnapped by Dr. Go, a mad scientist, and transformed into a cyborg with invincible steel frames and unlimited strength, the latest in a line of robot cats used for world domination, called the "Nyan-Nyan Army". He somehow, though, breaks a chip supposedly used to control him, and he escapes Go's laboratory as well as destroying it, while he now realizes that he is now bipedal and can speak human language. He comes to terms with his predicament, while maintaining his lifestyle as an average housecat. However, Go feels that Kuro is ungrateful to him, and he and the Nyan-Nyan Army, including the most well-known M, set out to find and kill him, though they eventually surrender and decide to live a more peaceful life.