Proto Man is Roll and Mega Man's brother and Dr. Light's robot son. One day it was peaceful in Dr. Light's lab. Mega Man had just finished beating Dr. Wily, when out of nowhere Fusions burst through the door and destroyed Proto Man and most of Dr. Light's other robots, except Mega Man, Roll, Rush, and Dr. Light himself. Proto Man's body is the only robot body that is left. Players can find three Dexbots in the wreckage of Dr. Light's lab trying to fix Proto Man; Dexter sent them there so they could bring him back to life to help out against the invasion.