Ryumanjisen was a Zionite as well as a crewmember of the Saltpillar, which was captained by Neoteny. He, like all of the other members of the ship's crew, were seen in the Recursion instance of The Matrix Online.
Prior to joining Neoteny's vessel, Ryumanjisen (often referred to simply as "Ryu") was the captain of the Ronin and co-leader of the Kings of Never alongside Dupz. Ryumanjisen had a long record of service as a Zion operative, extending back to the first days of the Truce.
Born as Steven Grim, little is known about his days a bluepill. After his extraction, Ryu was known for his martial prowess and his obsession to improve his martial skills. According to his particular mix of buddhist and zen philosopies, the Matrix was the place where someone could achieve "perfection". Ryu devoted himself to find that perfection.
Ryumanjisen often showed distrust for the Machines and when the Truce finally fell, Ryu had no issue aligning himself with Neoteny's militant campaign against them.