Null or Un, born Ulrich Koriyama, grew up as a normal little boy. His older brother, however, changed all that when Ulrich saw him shot in a gang related killing. He was eight years old. From then on, he vowed to never cause another person pain in the way his brother and the gangs had caused it. He also developed a strong sense of justice and began calling himself "White Knight" at school, much to the hilarity of his classmates. In fourth grade, a teacher's husband came in for career day and shared about his life as an "officer of the peace". Put off by the gun, but enthralled by the idea that jobs could involve protecting the innocent, he poured himself into the research of careers in law enforcement. He eventually chose to become a detective. He worked himself extremely hard and achieved his goal, finally, at age fifteen.

Life was good once again for the young detective, until the day that he found out about kiras. He found out the hard way. Chasing a lead, Ulrich, or, Null as he had been called for awhile, and his partner Chelise came face to face with a kira when chasing a murder case. This particular kira still believed in guns. He had been injured by the police, and knew he did not have much time left, when he spotted the young team. He hid, then jumped out and grabbed Chelise. Putting a gun to her head, he demanded that Null shoot him, or he would shoot her. Null stammered that he didn't have a gun, and the kira tossed him his extra. Null protested that he didn't kill people, but the kira laughed and shoved his gun up against Chelise's temple, and started counting down. Tears running down his cheeks, Null begged him to stop, but he kept counting. Null pulled the trigger on three.

Shortly after that incident, his name cleared by "Justified self defense", Ulrich moved. He also took up cello playing. He discovered that cello was the only thing that could drive the pain away. Terrorized by nightmares in which he was a "white knight stained red", he became amazing at the instrument by practicing late at night. Over the next two years he moved continuously, getting short-time jobs in detective agencies who were under staffed. He just recently settled down. Now he is seventeen, a young man who still believes in his vow, is terrified of causing people grief, and a man who had added another great mission to his past vow: "Save the kiras." He has promised that he WILL save at least one kira before he dies. From death, from destruction, and from themselves.