Janbu began as Michael Marsh's personal robot for school commutes until Dr. Kiwi forcibly modified it into the combat robot Galatt without Michael's knowledge or consent. To avoid punishment for illegal weapon possession under Dr. Kiwi's fabricated story of benevolent alien control, Michael had to conceal Janbu's new identity as Galatt. Before modification, Michael's classmates dismissed the robot as outdated, worsening Michael's social isolation.

As Galatt, Janbu became Earth's primary robotic defender against the alien Space Syndicate, using enhanced capabilities to battle destructive Armoroboids. It operated alongside two similarly modified civilian robots, Patyge and Kamige. Galatt's activities included temporary disappearances, such as during an encounter with a master thief.

Janbu functioned solely as a piloted mecha throughout its documented episodes, showing no significant autonomous personality, internal conflicts, or expanded background. Its narrative role centered entirely on being Michael's transformed robot, with no appearances or developments in sequels, movies, OVAs, or spin-offs indicated.