Jinnai Yodogiri

Yodogiri Jinnai was formerly the head of Yodogiri Shinning Coroporation which was the talent agency Ruri Hijiribe worked for. In reality, he is a very sly information broker and is even more skilled at manipulating others than Izaya Orihara is. He is wanted by both the Police as well as the Awakusu but evades capture every time. He is responsible for many of the events that occur in the series past volume 4 and can be considered the main antagonist overall.

Characteristics
Not much is known about Yodogiri in terms of both personality and physical appearance. All that is known about him is that he is middle aged, presumably in his 40s, and that he is extremely good at what he does. He also has plastic surgery regularly in order to keep his pursuers from finding him. The picture featured above may even be out of date due to the events that occur during Volume 08. Shingen also compares Yodogiri to a radioactive substance; those who get near him slowly start to decay and eventually die.

Background
Very little is known about his past or his early life but he is responsible for much more than the incident with Ruri Hijiribe. Before the series starts, Yodogiri is apparently the one who sold the Demon Blade Saika over to Shingen Kishitani and is also the one who convinced him to steal Celty's head. His motivations for this are unknown.

Light Novel
Volume 04 : Yodogiri is only mentioned in Volume 04 by several members of the Awakusu who are searching for him. He abandons his facade as the head of his talent agency and goes into hiding.

Volume 05 & Volume 06 : In another scheme of his, Yodogiri hires Russian Assassins Vorona and Slon to kidnap Akane Awakusu, the granddaughter of the head of the Awakusu for an unknown purpose, but his plans are thwarted when Akane unexpectedly comes into contact with Izaya. Izaya uses Akane to try to kill Shizuo Heiwajima which complicates the mission and causes its failure.

On top of this, he also realizes that Izaya had sent Masaomi Kida and Saki Mikajima to dig up information about him. To keep from being found as well as to get back at Izaya for thwarting his plans. Yodogiri calls Izaya on his cell phone and verbally taunts him for several minutes before stabbing him in the chest. He leaves Izaya bleeding on the sidewalk and runs off before anyone can notice him.

Volume 08 : (NOTE: the information on Volume 08 is limited so there are many details that are left out) Yodogiri sends a man named Adabashi Kisuke  to go after Ruri. His plans are thwarted this time by Mikado who lights Adabashi on fire and sends him screaming into the night. It is revealed at the end of the novel that Yodogiri is working very closely with Seitarou Yagiri, the uncle of Namie and Seiji. Their main goals are:

Volume 10: He sends Slon after Izaya to finish him off. It is also revealed that Yodogiri Jinnai is actually an identity used by a group of people as opposed to a single individual. The original Yodogiri Jinnai died several years ago but his Identity was still being used by his "secretary" Kujiraki, for her own purposes.
 * 1) to obtain Saika and it's current wielder, Anri Sonohara
 * 2) to reclaim Ruri Hijiribe, the half vampire (according to the subtle references to this fact that are given in the volumes)
 * 3) to reunite Celty and her head regardless of whether she wants to or not or what will happen to her afterwards.