Nakura was a student at Raijin Middle School along with Izaya and Shinra. After a "certain incident", Izaya forced Nakura into being an unwilling accomplice to many of his schemes.
Characteristics
Nakura in middle school demanding his money back from Izaya
Nakura is shown to be fairly average in appearance, having short brown hair and being rather thin. Before he had surgery to change his face in an effort to cut ties with his past, it was said he had identical moles on either side of his face near his eyes.
He is shown to be very greedy but not very smart as he lost all of his parents money making bad bets in a gambling ring he helped create. In the present day, he is shown to be very depressed as he is constantly being used as a convenient servant for Izaya's whims, lamenting that he may never escape him.
Background
After founding a biology club with Shinra, Izaya created a gambling ring in which Nakura was a member. Nakura continually lost money, threatened other members who had won, and even stole from his parents in order to keep gambling. On the last day of summer vacation, desperate and irrational, Nakura stormed into the biology club room with a knife, threatening Izaya to give him all the money he lost.
Nakura panics after having stabbed Shinra accidentally
When Izaya casually refused, Nakura rushed at him to attack. Shinra, who had been arguing with Izaya just before Nakura entered the room, jumped in the way of the knife and got stabbed as a result. In a panic, Nakura fled, and Izaya decided to use this opportunity to officially take the blame for the incident and blackmail Nakura from then on.
What's shown of Nakura's current face after facial surgery to remove his identifying moles
Nakura has since then been an unofficial and unwilling accomplice for many of Izaya's endeavors. During high school, the two of them revived their old gambling ring and named it "Amphisbaena." The group expanded but Izaya and Nakura abandoned it due to Izaya getting bored.
During college, the two of them also formed a "Experimental Legal Drug" that eventually became Heaven's Slave. They formed the club with another student named Hiroto Shijima who was very adept at experimenting with strange substances.
After college, Nakura continues to have contact with Izaya. He lets Izaya use his name, forwards mail packages for him, covers for him when others call to ask for information, and even appeared before Akane Awakusu under the name "Izaya" in order to trick her. It is also hinted that Shinra performed facial surgery on him at some point.
History
Dragon Zombie Arc
After the incident with Amphisbaena has passed, Izaya calls Nakura to update him on recent events. He states that the group "Amphisbaena" which had expanded without their knowledge, began encroaching on the Awakusu's territory thanks to one of their old "associates" who was nicknamed "Mimizu." When "Amphisbaena" was first formed, Nakura and Izaya both used fake identities with Nakura's alias being "Lizard." Mimizu used the "Lizard' persona as the false leader of Amphisbaena so that he would take the blame in case things went south. Izaya also explains that their old friend, Shijima, had entered into drug dealing and was selling a new and hyper-addictive drug called "Heaven's Slave."
When the drug club was formed, Nakura used the alias "Kumoi" which Shijima also used as a scapegoat when he formed the Heaven's Slave group. If the Awakusu resorted to having a gang war with either Amphisbaena or Heaven's Slave, then it would be Nakura who ultimately took the heat. Izaya explains that, since he effectively neutralized both groups, Nakura no longer to worry about being killed by the yakuza.
Nakura laments being under Izaya's thumb.
After Izaya hangs up, Nakura yells and screams about how horrible his situation is and how he will continued to be indebted to Izaya for the rest of his life.