Created to protect Dr. Otoi's grandson Nobuhiko, the robot Signal turns into a chocolate-loving baby every time Nobuhiko sneezes. When an enemy reprograms Signal's brother Pulse to become a killer, Signal must carefully guard Dr. Otoi's home. Armed with the latest weaponry and ordered to steal Dr. Otoi's most advanced robot technology, Pulse attempts to wreak havoc in the doctor's house, which is full of people, robots and animals.