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Though the main rules cover the Death Note's basic function, several secondary rules govern how the Death Note operates in conjunction with other Death Notes or how it can be used. Light uses the second rule to prevent the team from destroying the Death Note. Light uses the first rule to convince the investigation team that because the killings had stopped for two weeks while he was imprisoned, he could not possibly be Kira.
If the Death Note is burned, torn up, or otherwise rendered useless, any people who have touched the Death Note will die. If the owner of a Death Note does not use the notebook after 13 days time, he or she will die. They were written by Ryuk but are completely false. These rules were written in the Death Note to aid Light in a scheme he came up with to clear his and Misa's names. If a death note is lost or stolen the owner will lose ownership unless it is retrieved within 490 days. A death note will be rendered useless if the victim's name is misspelled four times. The Death note will not affect those under 780 days old. After writing the cause of death, the details of the death should be written in the next 6 minutes and 40 seconds (400 seconds or approx. If the cause of death is not specified, the person will simply die of a Heart attack.
If the cause of death is written within 40 seconds of writing the person's name, it will happen. Therefore, people sharing the same name will not be affected. This note will not take effect unless the writer has the person's face in their mind when writing his/her name. The human whose name is written in this note shall die. #Death note rules characters series
Before the series begins, Ryuk writes instructions in English inside his Death Note with the belief that English is the most popular language in the human world.