Light Yagami is an intelligent young man who resents what appears to be a relentless increase of crime and corruption in the world around him. His life undergoes a drastic change when he discovers a mysterious notebook, known as the "Death Note", lying on the ground. The Death Note’s instructions claim that if a human’s name is written within it, that person shall die, as well as various other rules. Light is initially skeptical of the notebook’s authenticity, but after experimenting with it using criminals, he realizes that the Death Note is real. After meeting with the previous owner of the Death Note, a shinigami named Ryuk, Light plans to become a god and establish a new world order by passing his keen judgment on those he deems evil and anyone who gets in his way.
Soon, the number of inexplicable deaths of reported criminals catches the attention of International Police Organization and a mysterious detective known only as "L". L quickly learns that the serial killer, dubbed by the public as "Kira" derived from the typical Japanese pronunciation of the English word "killer"), is located in Japan. He also concludes that Kira can kill people without laying a finger on them and that he is in Japan, after he uses a convicted criminal named Lind L. Taylor whose capture was kept secret, and who was condemned to die at that hour, pretending he is L so Light kills him. Light realizes that L will be his greatest nemesis, and a nuanced game of psychological cat and mouse between the two begins.
L realises Kira is getting information from inside the task force and sends 12 FBI agents to follow people connected to the Japanese police. Light tricks Raye Penber, his tail, into showing his ID, after which he kills all the FBI agents. Naomi Misora, Raye’s fiancee, suspects Kira was one of the people he tailed, but Light finds out and makes her commit suicide using the Death Note.
Misa Amane, another Death Note owner, finds Light, after sending a video in which she claims to be Kira. She possesses Shinigami eyes which allow her to see a person’s name and Lifespan, but cost half her remaining life. Obsessed with Kira after the death of her parents’ murderer, she devotes herself to helping Light, but is captured by L. Light makes a plan involving renouncing ownership of both Death Notes and all of his memories of them, and turns himself in to L for surveillance, as Rem threatens to kill him if Misa is not freed. Together, Light and L investigate eight people from the company "Yotsuba" who are using a Death Note for their own profit. While arresting the third Kira Higuichi, Light recovers all his memories when he touches the Death Note. He remembers and continues his plan of compelling the former owner of Misa’s Death Note, the shinigami Rem, into killing L and his aide Watari, which kills Rem as a Shinigami cannot purposely extend a human’s life. Light then gets her Death Note. Meanwhile, Misa again acquires the Shinigami eyes from Ryuk.
After L’s death, Light is given the position of the "new L" by the Japanese Task Force. Four years later, Near and Mello – two children who were raised to be successors to L in an orphanage founded by Watari – appear, with the goal of finding Kira. In the meantime, Kira has gained much public support, and has contacts. Mello, one of L’s successors who has joined the Mafia, kidnaps the Director of the NPA, but after Kira kills him, he kidnaps Sayu Yagami, Light’s little sister, as a bargaining chip to get the Death Note. The Japanese Task Force plans to go to Los Angeles to rescue Sayu but ends up losing the Notebook. The Task Force later attempts to retrieve it and succeeds in doing so, they also get Mello’s real name. However, as a result of an explosion that Mello uses to cover his escape and one of his henchmen, Light’s father Soichiro Yagami dies.
Near begins to suspect the second L of being Kira thus causing some members of the Japanese task force to also openly suspect him. Realizing the risk of being caught, Light has Misa give up ownership of her Death Note. He then finds his next successor, Teru Mikami, a strong, almost crazed Kira supporter, who kills Kira’s last spokesman for their greed which helped Near escape from a crowd of Kira supporters. Mikami later recruits a new spokesman for Kira, Kiyomi Takada, a newscaster and one of Light’s former college girlfriends. Teru Mikami and Kiyomi Takada continue killing criminals while Light is unable to do so himself. Kiyomi is later kidnapped by Mello and is forced to kill him with a hidden piece of the Death Note. Light kills Kiyomi to avoid her implicating him after she uses the note to kill Mello. Mikami, unaware of this action, writes her name in his notebook, exposing it to the members of the SPK. Near has it replaced with a fake notebook and, in a final confrontation with Light, is able to use it to prove that Light is Kira. Realizing that Light had lost, Ryuk writes down Light’s name in his own notebook, killing him with a heart attack.
The main character in Death Note, Light is an extremely intelligent, yet bored 17-year old student who is not satisfied with the current justice system. When he finds the Death Note intentionally dropped in the human world by the shinigami Ryuk, he decides to use it to kill criminals. He earns the title Kira, the Japanese pronounciation of the English word killer. His ultimate goal is to cleanse the world of evil and create a world without criminals. He intends to reign over this new world as its "god" and goes mad with power.
