In Death Note, the Death Note grants control over life and death: any person whose name is written in the book dies. In a perfect world, a Death Note would never have ended up in human hands, let alone those of someone as cunningly evil as series protagonist Light Yagami, the man who would build his legacy under the name Kira. With such immeasurable power at his pencil-tip, it would seem a given that Light is unstoppable, and if using the Death Note was as simple as writing down a name and calling it a day this would certainly be the case.
At numerous junctures throughout Death Note, Light is introduced to various rules that serve as stipulations for use of the supernatural book. These rules and conditions serve as a check and balance system of sorts, serving to at least sprinkle a touch of difficulty onto Shinigami-endorsed, mass killing sprees via a notebook. Here are some of the rules and limitations of the Death Note.
When executing a kill, in addition to a name, the user must also have the target’s face in mind. Death will not occur if these requirements are not met. Possessing a visual of the target’s face allows the book to specify the target amongst the hundreds of thousands of people with identical names. The Death Note will not affect those under 780 days old, those aged 124 years and older, or those with less than 12 minutes of life remaining naturally.
The Death Note grants its user manipulation of time of death, cause of death and the events leading up to a target’s death. The cause of death must be entered within 40 seconds of writing a name, at which point users have six minutes and 40 seconds to specify a time of death as well as events leading up to that death. Unlimited amendments to these details are allowed so long as they occur within the allotted time limit of their writing but require the user to rule out the original details by crossing them out with two straight lines.
The order in which cause of death and name are written is negligible so long as the name is written in front of the cause, and users have 19 days to fill in a name after a cause is written.
A target will automatically die of a heart attack if a cause of death is not specified 40 seconds after a name is written; the specified cause of death would influence or cause the death of unintended victims; a target with only two days left to live naturally is slated to die past that two day period, and/or if a timeframe is specified for a death involving a disease that would require more time to naturally develop than said timeframe would allow.
After obtaining the notebook its user is haunted by the Shinigami that originally owned it until said user’s death. This Shinigami can only be seen and heard by the book’s current host and anyone that touches the notebook. They are not allowed to intentionally distribute the notebook to humans below the age of six. In most cases, Shinigami enter the human realm out of sheer boredom or curiosity but are only allowed to dwell there if their notebook is in circulation or when searching for a target of their own. Barely possessing an understanding of the notebook themselves, Shinigami have no obligation to explain the notebook’s rules and affects to the inherited user unless asked.
Shinigami are required to carry a personal Death Note on their person at all times, and increase their life’s longevity by stealing the lifespan of those whose names they write down. Shinigami must avoid actions that would aid in or prevent the death of the targets of their current human host. Conversely, Shinigami that act to increase the lifespan of a human they favor by writing the name of that person’s destined killer will die themself.
The target of the Shinigami will still die, however, and the dead Shinigami’s remaining lifespan will be added to that of the human they saved. A Death Note continues to exist and maintain its power even after the death of its original Shinigami, with possession typically falling to the notebook’s last human host or the next Shinigami to happen upon it.
Shinigami Eyes automatically display human names and lifespans, but more than half of a targets’ face must be visible. (See the above chart for angles that meet the criteria.) Shinigami can give their current host the option to obtain Shinigami Eyes in exchange for half of that person’s lifespan. As the possession of multiple Death Notes is possible, this deal can be struck more than once. Each time a human agrees to sacrifice half of their lifespan. The collected lifespan is then added to that of the Shinigami with which the deal was struck.
As multiple Death Notes can be in circulation at once and there exist multiple causes of death it is not impossible for unique circumstances to arise. While the Death Note can only operate within a 23-day timeframe, this rule can be bypassed if death via a specific disease is listed without a set timeframe. In this instance, the disease would develop naturally and kill the target even if more than 23 days are required to do so.
Victims whose names are mistakenly misspelled four times become immune to the Death Note’s influence, but in the case of a name being purposely misspelled four times the user themself dies. In the latter case, the target is not granted immunity to the Death Note. When the same name is written in two notebooks, the details of the first entry will take priority unless the separate entries are within .06 seconds of each other, in which case the writings are considered simultaneous and the death is rendered null.
In the case of users possessing two notebooks, writing a name and cause of death separately in each notebook will still produce the desired outcome.
Originally it is stated that for Death Note users there is no heaven or hell after death only Mu, or “nothingness.” However, series author Tsugumi Ohba has confirmed that, in fact, all humans in the Death Note universe enter Mu upon death.
The Death Note grants its user the ability to control life and death but remembering all of the rules that govern its usage can be daunting.