In Tokyo, a high-school student named Light Yagami finds a “Death Note”, a mysterious notebook which can kill anyone as long as the user knows both the target’s name and face. After verifying that the notebook works, Light sets out to create a utopian world without evil, killing numerous high-profile Japanese criminals. Light is visited by Ryuk, a demonic Shinigami (death god) and the Death Note’s previous owner, who dropped the notebook into the human world out of boredom. Ryuk, who is invisible to anyone who has not touched the Death Note, is amused by Light’s vision and serves as Light’s companion.
As numerous criminals and convicts around the world die, the global media dub the mysterious god-like figure responsible for the murders as “Kira”, a Japanese transliteration of the word “killer”. Hoping to apprehend Kira, Interpol request the assistance of the enigmatic detective L to assist them in the investigation. After deducing that Kira is based in Japan, L stages a TV broadcast in which he tricks Light into revealing that he is in the Kanto region of Japan. He does this by having a death row inmate pretend to be him, and then broadcasting the news cast to specific regions in Japan but claiming they are country wide. Light kills the death row inmate during the broadcast, letting L know that he is in the Kanto Region. Humiliated, Light vows to eliminate L, whom he views as obstructing justice. L quickly deduces that Kira has inside knowledge of the Japanese police’s investigation, led by Light’s father, Soichiro Yagami. The FBI send a team of agents to monitor the families of those connected with the investigation, but Light outmaneuvers and kills them all. Nonetheless, L picks up enough hints to designate Light as the prime suspect. Around this time, Light graduates from high school to college. L recruits Light into the Kira Task Force, both trying to get the other to reveal crucial info.
At this point, a famous model/actress named Misa Amane gains a second Death Note from a Shinigami named Rem. Misa makes a deal with Rem for Shinigami eyes, which allows her to kill knowing only the face at the cost of half her lifespan. Misa commits numerous murders, sends taped recordings to the police, and eventually uncovers Light’s identity as the original Kira. Infatuated with Light, she demands Light be her boyfriend. Although he does not love Misa, Light agrees, intending to use Misa’s Shinigami eyes to discern L’s true name. However, before she can do so, L deduces that Misa is the likely second Kira and detains her. Rem, who has feelings for Misa, threatens to kill Light if he does not find a way to save Misa. Light arranges a scheme in which he and Misa temporarily lose their memories of the Death Note, and has Rem pass the Death Note to a less morally-driven individual, Kyosuke Higuchi of the Yotsuba Group. Now with no knowledge of the Death Note, Light wholeheartedly joins the investigation. Together, Light and L deduce Higuchi’s identity, arrest him, and discover the existence of the Death Notes and the Shinigami. When they touch the Death Note, Light and Misa regain their memories, and Light kills Higuchi with a piece of the Death Note, regaining ownership of the book. However, L casts suspicion on Misa, forcing Rem to murder L to save her. Rem dies in the process, as it is forbidden for Shinigami to protect human individuals. The task force agrees to cover up L’s death and appoint Light as the new L. The investigation stalls as a result.
Four years later, crime rates worldwide have massively dropped, but cults have arisen which worship Kira as a literal god. Two intelligent young men, who were raised as potential successors to L, are revealed: Near and Mello. Both are aware that L is dead, and thus consider Light, the current L, a prime suspect. Mello, along with the Mafia’s assistance, kidnaps Light’s sister, resulting in his father’s death during the rescue mission. As suspicion starts to fall again on Misa, Light passes Misa’s Death Note to a fervent supporter of Kira, Teru Mikami. He also appoints a well-known newscaster, Kiyomi Takada, as Kira’s public spokesperson. Realizing that Takada is connected to Kira, Mello kidnaps her. Takada kills Mello with a hidden page of the Death Note, but is killed by Light, in order to dispel suspicions. Shortly after, Near deduces Mikami’s connection to Kira and arranges a meeting between Light and the current Kira Task Force members. Light seizes the chance to have Mikami kill Near as well as all the task force members. However, Mikami’s Death Note fails to work. It is revealed that Near had replaced Mikami’s Death Note with a decoy. Perusing the names Mikami had written down, only Light’s is missing, which proves Light as Kira. A scuffle breaks out during which Light is grievously wounded. Ryuk, realizing that Light will spend the rest of his life in prison, writes down Light’s name in his Death Note as he had promised to do at the beginning of the story.