Fuji is a giant, and so is considered a freak by everyone around him it is unknown if he has a real name.
What is known of his past is that one day he was attacked and almost killed by a mob but the old man Saizuchi found him and took him in.
The gentle, depressed Fuji was in an ideal state for Saizuchi to manipulate his emotions and turn him into an unbelievable fighter. Saizuchi keeps telling Fuji that he owes him for saving his life and uses that to control him.
He was easily defeated by Hiko Seij?r?, though he spared his life. He was also the first to look at Fuji as someone other than a monster.
Upon capture, the Meiji government assigned him to northern Hokkaid? to develop land and act as a defending fighter during times of war.