Ryu's mind is still on the war and its food rationing, and he hates seeing food wasted. It is implied that he and his brothers orchestrated several different robberies in Tokyo, never with the intention of injuring someone. Their main goal was to rid the world of weapons of mass destruction, which they did by stealing military blueprints and burning them. After Tatsu is killed during Tetsujin 28's revival, Ryu decides that the best option is to try and knock Tetsujin down. Ryu gets into a truck, along with Tatsu's body, and drives into Tetsujin's leg. He dies after the truck is partially crushed and burned.
At one point, Ryu told Kenji that he could only depend on one weapon, this being Kenji's knives, which set the younger brother off of using guns. In the very last episode, Ryu appears as a ghost to tell Kenji not to be afraid to attack the PX Syndicate with guns, and to not feel so guilty about his and Tatsu's deaths.
In the Manga Edit
Although english information of the manga is unconfirmed, it has been said that Ryu was either the leader of a criminal gang and Kenji his assistant, of the two were government agents. What is clear is that Ryu was still Kenji's personal role model and advisor, but when he and another person are killed during their work, Kenji is left to finish the job.
Ryu's death was briefly alluded to in the Japanese version of the 1963 series, but it was mostly edited out of mention in the dub.
In the 2007 Movie Edit
In this version, Ryu is still alive after dropping out from the kamikaze pilot squad, and he and Kenji are the leaders of a small gang. When the war was still on, he briefly met Tsukie and learned about the Tetsujin project, but Tsukie promptly shot him afterwards. "Shoutarou" was his best friend in the pilot squad, and in the modern day, "Shoutarou" and Shotaro go to Ryu for help against Tsukie. One of the more famous scenes in the movie is when Ryu flies a small plane with "Shoutarou" standing on the back of the fusilage, armed with a sword.