Robotics expert Dr. Otoi built Signal to be a powerful companion for his young grandson, Nobuhiko. However, a mishap during Signal's programming led to an unexpected glitch. Every time Nobuhiko sneezes, Signal transforms from a temperamental adult robot into an adorable, chocolate-loving little baby.

Despite this little problem, days are usually happy and fun around the Otoi household, where robots, people and animals live in harmony. Except for the occasional feud over house cleaning chores or the affections of the female robot Elara. everything is relatively peaceful.

However, one day Signal is attacked by Pulse, one the Doctor's previous creations and the prototype for Signal. Despite being critically nearsighted, Pulse is loaded down with weapons and has been reprogrammed by Dr. Otoi's mysterious rival. He's on a mission to steal the most recent robot technology, and obliterate anything that gets in his way.