King Nipper, also known as Nipper, ruled Mechano City after originating as Dr. Daigo Tatsuro's robotic assistant—linking him to Yakumo's father and humanity's pre-catastrophe science. Following global upheaval, he governed the technologically advanced domain for centuries. During Yakumo, Mushra, Sago, and Kutal's journey, Nipper recognized their mission and Yakumo's status as the last human. He granted critical assistance by enhancing their abilities, unlocking their Ultra Hyper Form to combat formidable foes. Beyond technological empowerment, he offered refuge and strategic aid against threats like Lord Caris, servant of the Bird Queen Rusephine.

In a pivotal confrontation, Nipper sacrificed himself to shield Yakumo from Lord Caris, directly thwarting her assassination but resulting in his destruction by Caris. This act ended his centuries-long existence, marking his endurance through eras of profound change. His legacy intertwines with Mechano City's technological heritage and his essential role in empowering the protagonists against the Enterran generals during their struggle for peace.