Death Note (object)

A Death Note is a supernatural notebook used by the Shinigami to sustain their life, as well as a principal figure in the Death Note series.

Appearance
The appearance of a Death Note is decided by its Shinigami, and there are several different Death Note designs. Most Death Notes, such as Rem's, are plain black and do not have writing on the cover, but Shinigami occasionally write their name on it as a joke. Other cover designs may exist as well, but that would be completely up to the Shinigami owning that particular Death Note. The rules for the Death Note listed in the manga pilot chapter included in Death Note 13: How to Read state that nothing written on the cover by a Shinigami can be erased. Humans are able to write their names on the cover without dying, but this is not recommended. In addition, the pilot chapter's rules state that "if the cover is destroyed, the notebook cannot be used."

Death Notes with red or white covers exist but only appear in the live-action adaptions. Death Notes can also take a form other than a notebook, such as a scroll in Old Japan or like the Old Testament in medieval Europe. The inside of a Death Note looks like that of a school notebook and contains ruled white pages. The notebook is activated when a human's name is written in it. Regardless of how many names are written in it, the notebook will never run out of pages. Death Notes are made from an unknown material, however, they feel and look like regular notebooks, and it is possible to rip and burn the pages. Human science cannot analyze a Death Note.

Overview
The purpose of the Death Note is to take human life, thereby increasing the lifespan of the Shinigami who uses it. There are many rules governing 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."

Use by Shinigami
Shinigami normally use Death Notes to kill humans that they see through the observation hole in the Shinigami realm, thereby adding each human's remaining years of life to their own out of fear of dying themselves. Rogue Shinigami occasionally drop extra Death Notes from the Shinigami realm down to the human world, allowing a human the use of their spare killer notebooks. It is unknown how many notebooks exist in the Shinigami realm, as well as how Death Notes are created.

Use by humans
A Death Note can be used by a human, although their lifespans do not increase by doing so. Historically, humans have either killed other humans with the Death Notes or ended up burning and therefore destroying the Death Note for any number of reasons. Ryuk is the first rogue Shinigami shown in the series, though it is stated early in the series that there have been Death Notes dropped in the human world before.

Death Notes
A total of four notebooks are present in the Human World during the manga and anime series. These notebooks are listed here along with names of the people who gained ownership. Here, the notebooks are referred to using the name of the Shinigami who originally owned it. For example, the first notebook used by Light Yagami is called "Sidoh's Death Note."

How to Use It: The Complete Rules
This section reveals the rules governing the use of the Death Note. They have been divided into four parts: 1.) How to Use It, 2.) Ownership, 3.) the Shinigami Eyes, and 4.) the Shinigami Rules. Here, the rules will be explained by highlighting specific scenes from the series.

1.1 Entering Names

 * The Human whose name is written in this note shall die. This note will not take effect unless the writer has the subject's face in mind when writing his/her name. This is to prevent people who share the same name from being affected.
 * Use in the story: Realizing that people sharing the same name cannot be killed at once, L uses the name of an idol singer named Hideki Ryuga when he approaches Light.
 * The Death Note will not ever affect a person whose name has been misspelled four times.
 * When the same name is written in two or more Death Notes within 0.06 seconds, the entry is regarded as simultaneous; the Death Notes will not take effect and the individual will not die.
 * When the same name is written in two or more Death Notes, the note which was used first will take effect, regardless of the time of death.
 * If a Death Note owner accidentally misspells a person's name four times, that person will be free from being killed by the Death Note. However, if the Death Note owner intentionally misspells the name four times, the owner will die.
 * The Death Note will not take effect if the victim's name is written on several different pages. However, the front and back of a page is considered to be one page. For example, the Death Note will take effect if the victim's last name is written on the front page and first name on the back.
 * The Death Note will not take effect if the victim's name is written on several different pages. However, the front and back of a page is considered to be one page. For example, the Death Note will take effect if the victim's last name is written on the front page and first name on the back.

1.2 Entering the Causes and Conditions of Death

 * If the cause of death is written within 40 seconds of the subject's name, it will happen.
 * If the cause of death isn't specified, the victim dies of a heart attack in 40 seconds. However, the rule can be delayed for twenty-three days, meaning you can write down "dies by heart attack in [xx] days."
 * After writing the cause of death, the details of the death should be entered within the next 6 minutes and 40 seconds.
 * If the time of death is specified within 40 seconds after writing the cause of death as a heart attack, the time of death can be manipulated and can go into effect within 40 seconds after writing the name.
 * The conditions of death will not be realized unless they are physically possible for that human or could be reasonably assumed to be carried out by that human. Although it is possible to control a person's actions, if an impossible situation is written down the person will simply die of a heart attack.
 * Since the limitations applying to the conditions of a death are unknown to the Shinigami, Death Note owners must find out on their own.
 * You may write the cause and/or death prior to filling in the name of the individual. Be sure to insert the name in front of the cause of death. You have about 19 days (according to the human calendar) to fill in a name.
 * Use in the story: Light was able to wipe out all the FBI agents by writing their conditions of death ahead of time and having Raye write in the names.


 * After an individual's name, time of death, and conditions of death are entered in the notebook, the time and conditions of death may be altered as many times as desired as long as they are changed within six minutes and 40 seconds from the time they are filled in. But, of course, this is only possible before the victim dies.
 * If you write "dies of accident" for the cause of death, the victim will die from a natural accident six minutes and 40 seconds after the time of entry. "Accident" is a condition of death, so six minutes and 40 seconds are provided to write down additional details. The conditions do not take effect until this time has passed.

Trivia

 * Shonen Jump made Death Note notebook replicas, which can be bought from their website.
 * Misa's Death Note for the Death Note movie is also purchasable, and it comes with a pen.
 * In the 2019 video game Jump Force, it is shown that the Death Note loses its powers if the original universe it comes from merges with realities with other supernatural powers.