Mac Rosario is a megalo box fighter working under Shirato, a researcher under the ROSCO corporation.
Mac came to Japan on a boat as a young adult. He met Maya when she was working as a waitress. In his life Mac has been a boxer before quitting megalo box and starting a job as a police officer. After being fully paralyzed Sakuma from the ROSCO corporation reached out to Mac to become part of the research he was doing on gears and their medical uses for paralyzed patients. Mac stepped back into the ring after lots of training as a thanks to Sakuma and to prove to everyone that the gears truly helped him get back on track.