A brother of Kei and the terrorist of the resistance movement.

In the anime, Ryuu aided a terrorist attack on a shopping mall. He was then in charge of the team whose task is to infiltrate the military hospital, and find any information they can on the new subject, Tetsuo Shima.
When he shows up half-dead in front of Nezu to inform him of the hospital mission's failure, Nezu shoots him in a panic.

In the manga as the story progresses, Ryuu abandons his terrorist roots and becomes more heroic, working with George Yamada and guiding Shotaro Kaneda to Akira's chamber where Tetsuo Shima is held up, but battles with alcoholism.

Ryu shoots and "kills" Akira; elevator debris lands on him shortly afterwards.
(Source: Akira Wikia)