In The Manga Edit
Early on in the manga, Kenji and his older brother Ryuusaku were secret agents from the government, whom were sent after police officers and criminals. Not much is clear about their actual appearance, as the manga has never been translated and the Japanese Wikipedia page claims Ryu to be the leader of a crime gang. However, at one point, Ryu and another agent are killed, leaving Kenji to finish their work. Kenji would later appear on and off to help Shotaro and Otsuka out.
In The Anime Edit
1963 series Edit
Kenji is immediately introduced as a secret agent and Shotaro's ally in the 1960's version, whereas they clash many times in the later version. In the 1960's edition, he played a large part in finding important information for the group, and also in saving the day. Frequently, he would use special disguises or fighting techniques in order to get his work done.
2004 series Edit
In the 2004 series, Kenji and his brothers are briefly shown as wanted criminals who go after money and military weapon blueprints, the second of which they destroy, hoping to rid the world of large weapons. Their parents were killed by a firebombing, and as a result, it makes them hate war and weapons of mass destruction. They avoid harming others during their heists. When Tetsujin is accidentally activated, causing Tatsu Murasame and Ryu's deaths, Kenji pursues revenge against Shotaro by attempting to get rid of Tetsujin, and then the control box. At one point, he helps reunite Dr. Franken and his monster, and works with Thrill Suspense's gang. After some time, he becomes an investigative reporter and slowly becomes an older brother figure to Shotaro. After single-handedly shooting down the entire PX Syndicate (with encouragement by Ryu's spirit), he fakes his death in order to make Shotaro go through with the final stage of their plan. He uses throwing knives for self defence, once being scared away from guns after Ryu's suggestion.
Kenji clashes frequently with Ms. Takamizawa. She begins to develop affection to him after he performs CPR on her in episode 21, with her previously thinking of him as an untrustworthy degenerate, but the most he ever thinks of her is as a colleague. At one point, she begins to call him "darling", but he makes fun of this. In the last episode, Kenji gets her to keep quiet about his faked death by kissing her.
In Emperor's Emblem Manga Edit
Kenji appeared saving Shotaro and Alice Dragnet from an all-girl gang led by Nelke but he vanished after Tetsujin 28 defeated Nelke's Bacchus. In the Superhuman Kelly chapter, he was seen going to the restaurant. There, he and Nelke discussed about the robot Gilbert, Dr. Dragnet and his children, Kelly and Alice. Later, they protected Shotaro and confronted Kelly, who later escaped with Alice with him. Kenji reappeared saving Shotaro but has injured when Kelly shot him in the arm. When Nelke died sacrificing herself to kill Kelly, he and Shotaro mourned her death. Afterwords, while recovering his injuries, Kenji thanked Shotaro and Alice for their everything and said goodbyes to them.
2007 movie Edit
In the 2007 movie, he and Ryu are the leaders of a small criminal gang, with Takamizawa as their closest lackey. Kenji is dating Takamizawa, but is dismayed when she begins to shower Shotaro with affection (as she's a Shotacon - pedophile - in this movie). Kenji still manages to save Shotaro from being crushed during a robot fight.
In Other Media Edit
Giant Robo (OVA) EditKenji Murasame is one of the International Police Organization's top three agents, his special ability being immortality. In one rather famous scene, he shoots himself in the head, and sits up moments later. His other abilities include running extremely fast and special disguises.
He is hinted at having romantic feelings for Ginrei, whom he rescues twice, and even burns his entire body by breaking down an energy forcefield, just to let her get through to Genya's chambers.
He appears in only one of the three Ginrei Specials, but it turns out that he was Ginrei in disguise for nearly 85% of the special.