Maki was the daughter of a brilliant Professor of robotic science who desired nothing but to use his knowledge to help humanity. Maki inherited her father's scientific talent, and they worked together as a team. The duo developed many miraculous inventions such as HazMat gear, cybernetic enhancements, and robotic drones designed for deep space exploration. Despite all of his brilliance in ingenuity, Professor Oyamada was a lousy businessman and allowed himself to be controlled by the greedy Negata Corporation. When Negata himself demanded immediate repayment for the Professor's funding, Oyamada had no choice but to turn over all of his assets to Negata, leaving him in ruin.
The stress associated with his financial troubles eventually sealed Professor Oyamada's fate, and he died soon after. When Negata approached Maki with an offer to work for him once again, she couldn't bear to abandon her father's legacy and begrudgingly accepted his offer. Maki was further troubled by the fact that her inventions were being turned into and sold as military weapons, a far cry from their original purposes.
Sometime later, Maki encountered Lupin III, who declared to her that he was just as opposed to Negata's intentions as she was. Lupin and his gang offered to help Maki spread awareness of the dangerous potentials of her inventions and in doing so, help cease military use of them. Maki was enthusiastic of the idea and began collaborating with the thieves.
The groups first attempt at unveiling the robot was through a jewel heist, with Maki acting as LAMBDA's pilot. Following the successful heist, Lupin broadcast a televised announcement that it was him that had staged the robbery and was using government hardware to do so. Despite the successful operation, Maki felt remorse over the substantial property damage caused by Lambda.
The next afternoon, they sent out the robot again, this time to merely fly above the heads of the public. The army had been called in, however, intent on destroying the robot. Maki easily evaded their firepower but was concerned for the welfare of innocent bystanders and did her best to protect them from falling debris. She was eventually recalled by Lupin and immediately headed back to their base. Unbeknownst to her, she was followed by a suspicious bystander: Inspector Zenigata.
As he snooped around the abandoned tower, Zenigata was eventually captured by the Lupin gang. Feeling sorry for the captive, Maki provided him with hospitality, explaining her motives to him. Zenigata revealed that the man she was working with was not the real Lupin, but in fact Negata Jr., the son of her employer. Zenigata explained that they were using Maki for their own needs and had no intention of surrendering Oyamada's technology.
Negata Jr. gleefully confirmed the man's claims and took Maki away; at the top of the tower, Negata's thugs tied up Maki and stuffed her into the robot's cockpit, sending it flying into the sky as they detonated the tower behind it. Meanwhile, Zenigata managed to escape his confines and the building just in the nick of time, mounting LAMBDA and freeing Maki. He was then revealed to be the real Lupin, who had taken offense at his name being abused.
Inside Negata's main laboratory, Lupin and his gang confronted Negata and his impostors. After his thugs were swiftly taken out, Negata called a weaponized prototype of Maki's robot, SIGMA, to his aid but to his surprise, the robot began to wreck the facility instead. Maki explained that she had appropriated SIGMA's control device and overwritten its original programming, setting it to destroy the factory and then self-destruct.
As the factory went up in flames, Maki, along with LAMBDA carrying the restrained criminals, met with the real Zenigata outside. She turned the criminals over to the authorities and helped clear Lupin's name.
- Maki's Japanese voice actress was Sumi Shinamoto, who had previously (also under Hayao Miyazaki) performed the lead female role in the movie The Castle of Cagliostro.