Jijii is a very short, old man and the leader of a small band of exiles bent on destroying the notorious Anjou gang and making as much money as possible. To do this, he has taken a young man under his wing, whom he calls Ichi. Jijii has implanted false memories in Ichi's mind, which cause him to go psychotic. Jijii, in a sense, had made this cowardly young man into the ultimate killer.
In reality, not much is known about Jijii. What we do know is that, despite his old appearance, he is only 35. Plastic surgery and heavy steroid use caused him to look the way he does. His plans are much greater than simply the destruction of the Anjou gang. He is a sort of "super hero" of Shinjuku, basing his entire life to balance out the good and evil in the town. Well, rather, the greater evil and the lesser evil.