Akihiro's younger brother.

After both brothers were separated from each other by space pirates, Masahiro becomes a Human Debris mobile suit pilot for Brewers. While he remembers Akihiro's promise to find him, years of abuse have created a massive sense of pessimism and melancholy that eventually develops into insanity after Akihiro meets him a second time. When Akihiro urges him to defect and attempts to tell him there is still hope for them to have a brighter future, Masahiro snaps and believes that his brother had forsaken him when he learns that Akihiro found a new family in Tekkadan and had initially given up on him for a long time. He proceeds to lecture Akihiro on the fate of all Human Debris. Masahiro is killed when he pushes Akihiro's Graze Custom out of the way of a hammer strike from the Gundam Gusion, his Man Rodi being crushed against a chunk of space debris with the Gusion's strike. Before dying, he has one final face-to-face talk with his brother.
(Source: Wikipedia)