He is depicted as an old man, with a staff. He is one of Kurei's Uruha Death Squad members. The ten of them are the ten most powerful soldiers in Kurei's army. As his name suggests, he is a master of Genjutsu, or illusionary techniques. He is by far the 2nd weakest of the Jyushinshu, only Mikoto is weaker. He is perverted as he wants to have Neon as a sex slave (it hints it though), has no respect for life or believes in God only to create the most bizzare experiment possible.
Part in story
He originally battled against Kurei but lost terribly. He battled him again three years later, and was crushed again, at which point Genjuro referred to him as a demon. Kurei, seeing potential in him, made him one of the Uruha members. Genjuro appeared loyal to Kurei, even teaching him the Shadow Replication technique. However, his real purpose was to kill Kurei, and to take his powers. It was later found out that the reason Kurei formed the Uruha squad was to test the member's loyalty to him.
He entered the Ura Buto Satsujin as one of Kurei's Uruha squad. His team consisted of Shiju, Mokuren, and Meno with Genjuro being the leader. He used Meno as a doll with his Madogu, his staff which can shrink people. Meno had a time limit of 10 minutes to finish the match, otherwise her father would die in a quicksand tube. Hanabishi Recca attempts to attack Genjuro, but Neon's forcefield stops him.
Recca manages to get past her forcefield, and destroy Genjuro's staff, ensuring that no one dies in the fight. A mad Recca immediately challenges Genjuro to a match. Although Genjuro didn't have his staff, he used a Genjutsu technique to replicate himself and leave Recca unguarded. However, because he hated Kurei, he decided to use psychic surgery to extract Recca's dragons, but it backfires when Setsuna, the strongest of the eight dragons turns on him, and destroys him. Seeing that he was useless as well as a traitor, Neon kills him.
In the manga, however, Neon ended up killing his Shadow Replication instead, while he escaped. Genjuro sought refugee to Mori Kouran and helped him in the project of cloning Kurei, resulting the creation of Aoi and Renge. Genjuro was put in charge in one of the fortresses of SODOM City, in which he encountered Neon again. He first overwhelmed her with his robots, but got panicked when he saw Ishijima Domon seemingly allying himself with Neon and her sisters. While Genjuro was attempting retreat, however, Neon thwarted his escape and killed him for good using Jishou's blades.
He is able to copy himself to at least ten (which he passed this ability to Kurei), very agile for his age and uses physic surgery to take out diseases or unlock potential. Mugen (夢幻 Dream?) - A staff used by Genjuro of Uruha Maboroshii that allows its user to shrink living things by affecting its cellular structure. Its primary stone has the symbol illusion (幻 maboroshi?) written on it. However, he does not depend on it at all.