Death Note (object)

A Death Note is a supernatural notebook which is used by Shinigami to sustain their life.

Overview
The purpose of the Death Note is to take Human life, thereby increasing the life of the Shinigami who uses it. There are many rules as to how the Death Note can be used, though the most pivotal rule is that "The Human whose name is written in this note shall die."

A Death Note can be used by a human, although their lifespans do not increase by doing so.

It is unknown how many notebooks exist in the Shinigami Realm, as well as how Death Notes are created.

Use By Shinigami
Shinigami normally use Death Notes to kill humans from the Shinigami Realm, thereby adding each human's remaining years of life to their own.

Rogue Shinigami are Shinigami who drop extra Death Note(s) from the Shinigami Realm down to the human world in order to allow humans the use of their spare killer notebook(s).

Use By Humans
Historically, humans have either killed other humans with the Death Note(s) or ended up burning and therefore destroying the Death Note for any number of reasons. Ryuk is the first Rogue Shinigami that is shown in the manga, yet it is stated early in the series that there have been other Death Notes dropped in the human world before.

The Death Note is regarded by Near as the most deadly weapon ever used in the history of mankind.

Death Notes owned by Humans
A total of four notebooks are present in the Human World during the series. These notebooks are listed here along with names of the people who gained ownership. In this article the notebooks are referred to using the name of the Shinigami who originally owned it, therefor the notebook found by Light is called "Sidoh's Death Note". It is important to note that ownership is not the same as simply holding the notebook.

Sidoh's Death Note
Sidoh's Death Note was found by Ryuk, who dropped it into the Human World. The notebook was then found by Light Yagami in the courtyard of his high school in Kyoto, Japan. The rules of how to use it were written in it by Ryuk. This Death Note would ultimately change Light's life forever, turning him into a serial killer who targeted criminals.

Light gave ownership of this notebook back to Ryuk, who gave it to Rem, who was instructed by Light to give it to a greedy human who would use it for his own gain. It was given to Kyosuke Higuchi by Rem. After Higuchi gets captured by L, the Death Note ends up in the hands of the Japanese Task Force.

Soichiro Yagami later trades the Death Note to the Mafia, who kidnap Sayu Yagami and ask for the Death Note in exchange for her life. The Death Note was then given to Jack Neylon by Mello.

The Death Note is recovered by the Task Force and given by Light to Sidoh, who takes it back to the Shinigami Realm.

Gelus's Death Note
Gelus fell in love with Misa Amane, and used his Death Note to kill the man who was destined to kill Misa. Gelus died as a result, leaving only his Death Note behind. The notebook was found by Rem, who took it to the Human World and gave it to Misa, who Rem believed was supposed to have it. Light eventually has Misa give up ownership of her notebook, and it is sent to Teru Mikami. Mikami's notebook is later stolen by the SPK.

Rem's Death Note
Rem's notebook remains in her possession until her death. She uses it to protect Misa by killing Watari and then L. This act causes her to die, and her notebook is left behind, making it property of the Human World. Ownership of her notebook is taken by Light, who gives it Ryuk in order to make Ryuk the Shinigami attatched to it. Light then keeps it until he gives it to the Task Force to use against the Mafia. Soichiro becomes the holder of the notebook, and makes the trade with Ryuk for the Shinigami Eyes.

Ryuk's Death Note
Ryuk's notebook remains with him for the entirity of the series. It is not used until the very end, when he writes down the name of Light Yagami.

Differences between Death Notes
There are several different Death Note designs by Shinigami, including plain black (Rem's Death Note), English (Sidoh's Death Note) and a Shinigami language (Gelus's Death Note). Other cover designs may exist as well, but that would be completely up to the Shinigami owning that particular Death Note. There are other Death Notes which are red or white as well, yet they are never shown in the manga or the anime. They are more rare than black Death Notes, however, they have the same effects as black Death Notes.

Trivia
Shonen Jump also made Death Note notebook replicas which can be bought from their website, and Misa's Death Note for the Death Note movie is also purchasable, which comes with a pen.