Sidoh's Death Note

"This is the notebook that Ryuk picked up in the Shinigami Realm. He wrote rules into it and dropped it into the Human World. It passed through Light, Higuchi and Mello until finally being returned to its original owner."

- Death Note 13: How to Read

Sidoh's Death Note is the first Death Note seen in the series and the first notebook discovered and used by Light Yagami. This Death Note would ultimately change Light's life forever, turning him into the mass murderer Kira who targets criminals.

Appearance
The notebook has a black cover with the words DEATH NOTE written on the front and white ruled pages inside. Based on the side of the notebook that Ryuk wrote DEATH NOTE on, the notebook opens on the right side and apparently reads from left to right. The inside of the Death Note contains the basic rules of how to use it, which are written in English on the inside front cover. These rules were added by Ryuk just before the start of the series and were not originally present inside the notebook when Sidoh owned it. Light later has Ryuk write two fake rules in the Death Note, which Ryuk adds to the inside back cover.

The Rules
The five rules written by Ryuk are as follows:
 * “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 their mind when writing his/her name. Therefore, people sharing the same name will not be affected.”
 * “If the cause of death is written within 40 seconds of writing the subject's name, it will happen. ”
 * “If the cause of death is not specified, the subject will simply die of a heart attack.”
 * “After writing the cause of death, the details of the death should be written in the next 6 minutes and 40 seconds (400 seconds).”

Fake Rules
Light makes some small additions to the rules of the Death Note. He has Ryuk write them on the inside back cover of the notebook. Although the rules are fake and unable to take effect, their inclusion in the notebook allow Kira to stay one step ahead of L and ultimately defeat him outright.
 * “If the owner of the Death Note does not write a name in it for 13 days, consecutively, he or she will die.”
 * “If the Death Note is burned or destroyed, all who have touched it will die.”

Plot
Sidoh's Death Note was stolen by Ryuk in the Shinigami Realm. He added to it rules of how to use it and dropped it into the Human World. The notebook was found by Light Yagami on the lawns of his high school in Kyoto, Japan. Later in the story, Light gives his notebook to Ryuk, who gives it to Rem, who is instructed by Light to give it to a greedy human who would use it for his own gain.

As part of his plan to erase suspicion of him being Kira, Light turns himself in to the Task Force and says that there is a possibility that he might unconsciously be Kira. While being monitored in a prison-like cell within Task Force headquarters, Light signals to Ryuk that he is giving up ownership of the Death Note and loses all of his memories. It is then given by Rem to Kyosuke Higuchi. Because Light is incarcerated while Kira killings commence, L has no choice but to release him. Light begins working enthusiastically with L to find Kira, now unaware that he ever was the mass murderer. After L falls into self-declared depression because his "evidence" no longer adds up to Light being Kira, Light begins trying whole-heartedly to find Kira and eventually discovers a lead: the Yotsuba company. After Misa proves the identity of the new Kira, Light and L arrange for the arrest of Kyosuke Higuchi. The two arrive at the scene of Higuchi's capture, and when Light holds the Death Note, his memories return. Light holds on to the notebook in order to keep his memories (which would disappear if he let go), and he kills Higuchi using a piece of the Death Note he had hidden in his watch. With Higuchi dead, Light becomes the Death Note's owner once again. The Death Note ends up in the hands of the Japanese Task Force, while remaining under Light's ownership.

Soichiro Yagami later trades the Death Note to the Mafia after the kidnapping of Sayu Yagami. The Death Note was given to Jack Neylon by Mello, and although Mello holds the Death Note quite often and considers it his property, he never technically gains ownership of it. Following Jack Neylon's death, Roy picks up and gains ownership of the note, only to lose it soon after when the mafia building collapses and he dies.

The Death Note is recovered from the Mafia and returned to Sidoh, who takes it back to the Shinigami Realm. However, Light keeps pieces from Sidoh's Death Note and hides scraps in his watch, using them until his defeat.

In other media
In most adaptations, the notebook that Ryuk drops is not known to be taken from Sidoh. The anime is the only adaptation of the manga that shows it to be Sidoh's notebook.

Film series
In the film series, the notebook seems to be Ryuk's second Death Note, and Sidoh has his own two notebooks.

When Light sends Rem to find a new Kira, Rem takes Gelus's Death Note and Light buries his, so this is the notebook that Misa digs up and uses. Ryuk is the only Shinigami owner of this notebook. L eventually burns the notebook, mentioned at the end of Death Note: The Last Name and shown in L: Change the WorLd.

Despite being burned, Ryuk has the same notebook again in Death Note: Light Up the NEW World, which he again brings to the human world as one of the Six Death Notes. In the novelization, Sidoh has his own notebooks that are separate from this one.

The current status of the notebook is unknown in the film series, as some of the notebooks have been destroyed but others are being used, but which Death Notes survived is not specified.

Ownership Transfer:

Musical
In the musical, this notebook and Ryuk's Death Note are combined. In the end, Ryuk takes this notebook back and uses it on Light. Light is the notebook's only human owner. It is used by Light and FBI agent Haley Belle and is also touched by Misa and L.

2015 TV drama
In the 2015 television drama, the notebook seems to be Ryuk's second Death Note. This notebook is hardcover but otherwise appears the same. In the end, the notebook burns in a warehouse fire.

2017 film
In Netflix's 2017 film, the notebook seems to be Ryuk's. A prior user wrote in the notebook to not trust Ryuk, and it has had several previous users, indicating that Ryuk has had the notebook and has been giving it to humans for many years. The notebook has a much different appearance and includes many more rules written into it.

During the film, Light is the only human owner of the notebook. It is also used by Mia Sutton, FBI agent Raymond Young (while controlled by the Death Note, as written by Mia), and Aaron Pelts (while controlled by the Death Note, as written by Light). At the end of the film, it is suggested that L uses it as well.

Trivia

 * While not present in the manga, the rules page in Sidoh's Death Note has the Roman numeral for "one" placed under "How to use it."

Hiding the Death Note
Sidoh'n Death Note