Federal Bureau of Investigation

The Federal Bureau of Investigation, or F.B.I., is a governmental agency belonging to the United States Department of Justice serving as both federal criminal investigative body and an internal intelligence agency.

Plot
Throughout the series, there are various F.B.I. members shown, each playing varying roles. The first and most notable role they played was when twelve F.B.I. agents were sent to Japan to investigate the Kira murders, including F.B.I. agent Raye Penber, who was investigating Light Yagami, a prime suspect in the case.

Light ends up tricking Penber into showing him his F.B.I. identification card, revealing his name. With this information, Light later contacts Penber via phone, telling him that he is Kira and proving this by killing someone. He then threatens Penber, ordering him to get onto a train and pick up an envelope waiting for him there. Penber is instructed to write down the names of all the F.B.I. agents in Japan, and he does so, unaware that he is actually writing their names on a piece of paper from the Death Note, thus killing them all.

Having had all their agents in Japan die, Steve Mason of the F.B.I. states that his organization refuses to cooperate with L any further on the Kira investigation, and the F.B.I. backs out.

After the time skip, Steve Mason decides to tackle the case again, working with Near to create an organization known as the Special Provision for Kira, or the S.P.K., which consisted of members of the F.B.I. The majority of the S.P.K. members were later killed by Mello's subordinates with the Death Note.

Agents
L brings twelve FBI agents to Japan to investigate members of the NPA and their families: Raye Penber, Toors Denote, Haley Belle, Lian Zapack, Arire Weekwood, Ale Funderrem, Freddi Guntair, Knick Staek, Bess Sekllet, Frigde Copen, Girela Sevenster, and Nikola Nasberg. (In the anime, David Lincher is one of the twelve, replacing Freddi Guntair.) Raye Penber is assigned to observe the Yagami family, and Light finds out Penber's name. Light uses the Death Note to manipulate Penber into unknowingly killing the other eleven agents.

Steve Mason is a director of the FBI and, later, a member of the SPK. He works with L to bring the twelve FBI agents to Japan, but after their deaths, he pulls his support. He later works with Near to help establish the SPK. He dies during the killing of the SPK members.

Naomi Misora is an FBI agent who works with L on the Los Angeles BB murder cases. By the time the Kira killings begin, she's left her job in preparation to marry her fiance, Raye Penber. After Penber's death, she tries to get in contact with L to help with the Kira investigation. She dies when Light tricks her into revealing her name.

John McEnroe was one of the FBI agents working with the SPK. He survives the killing of the SPK members, but leaves after that and is not seen again. In the anime, he works with Near again later on but does not follow his orders.

In other adaptations
In the L: Change the WorLd live action film and novel, Hideaki Suruga is after L's Death Note, but switches sides to help L instead. In the novel, Robert Fairman is an agent meant to be Naomi's successor, and he works with Suruga to bring in confidential information.

In Death Note: The Musical, the arrival of the twelve FBI agents in Japan for the Kira investigation is announced on TV. Light finds Haley Belle's name because Belle's fiance put information about them online, and he uses the Death Note to make Belle kill the other FBI agents by writing down their names. Belle dies by jumping in front of a train, as written by Light in the Death Note.

In the Death Note television drama, the twelve agents in Japan are Mark Dwellton, Henneth Belle, Ryan Zapwack, Arrie Wheelwood, Thomas Denorold, Beth Skulmore, Frederick Marsmore, Nicholas Nethernburg, Ariel Feithston, Gabrielle Foughman, Knick Macburden, and Loyd Jr Foughman. The agent tailing Light is Mark Dwellton, who uses the aliases Raye Penber and Thomas O'Connor as covers. Dwellton's fiancee is Cathy Cambell, and Light uses this information to manipulate Dwellton into writing down the other agents' names in the Death Note. When Dwellton doesn't write down his own name, he confronts Light, who he now knows is Kira. Misa Amane writes down Dwellton's name in her Death Note, allowing Light to get away.