He's the true primary antagonist of the series and he's also bedridden and locked inside his room, guarded by two albino twins. Due to his state inside an old man's body, the managing duties of DW prison are left to Tamaki.
He's also a Deadman. He's killed by Shiro after challenging her Wretched Egg persona to a fight. It's later revealed that Hagire isn't actually dead, since he had transferred his memories to Sakigami Toto and is currently occupying Toto's body.
In the past, Hagire who was in his orginal body and was the head of the research facility Ganta's mother, Igarashi Sorae worked in. They led the research on the Nameless Worms and experimented on a little Shiro; while Sorae was plagued by guilt due to the inhuman experiments, Hagire was shown uninterested in Shiro's well-beings and often sadistically pushed the experiments forward. In the end, the pains from many experiments forced Shiro to create the Wretched Egg persona (which she termed "Ace Man", a hero who saved the weak on a TV shows she and Ganta watched together), and developed the ability to control blood. Hagire's interests in Shiro skyrocketed after the Wretched Egg appeared, and he started to aspire to be like her.
HIs branch of sin appears as tentacle-like whips, which he uses wildly and randomly, however, when he transfers to Toto's body, he gains Mockingbird's branch, Love Labyrinth