Death Note follows Light Yagami, a genius high school student who discovers a supernatural notebook dropped by a Shinigami (death god) named Ryuk. The notebook allows its user to kill anyone simply by writing their name while picturing their face. Light uses this power to cleanse the world of criminals under the alias 'Kira', triggering a global cat-and-mouse game with the enigmatic super-detective known as L.

The Death Note has many complex rules. The most fundamental are: 1) The human whose name is written in this note shall die. 2) This note will not take effect unless the writer has the person's face in their mind when writing his/her name. 3) If the cause of death is written within 40 seconds of writing the person's name, it will happen. 4) If the cause of death is not specified, the person will simply die of a heart attack.

L Lawliet, known simply as L, is the world's greatest detective and Light Yagami's primary antagonist. He is an eccentric genius who hides his identity and communicates through a laptop with a filtered voice. He is the only person capable of challenging Light's intellect, turning the series into a high-stakes psychological thriller rather than a simple supernatural story.

A Shinigami can offer a human the 'Shinigami Eyes', which allow them to see the name and remaining lifespan of any person they look at floating above their head. However, the cost of this trade is half of the human's remaining lifespan. This creates a major moral and tactical dilemma for the characters throughout the series.

The 2006 anime is a faithful adaptation of the original manga set in Japan, praised for its psychological depth and chess-like battles of wit. The 2017 Netflix film is a loose American adaptation set in Seattle, which significantly altered the characters' personalities, the plot, and the tone, receiving largely negative reviews from fans for simplifying the complex themes of the original.

Ryuk, the Shinigami who dropped the notebook, is addicted to apples from the human world. He describes them as being 'juicy' and superior to the withered, sand-like apples found in the Shinigami Realm. For Ryuk, apples are equivalent to cigarettes or alcohol for humans; he even suffers withdrawal symptoms if he goes too long without one.

Death Note explores deep philosophical themes including the nature of justice, the corruption of power, and moral relativism. It asks whether the end justifies the means (killing criminals to create a peaceful world) and examines how absolute power can warp a person's morality. It also critiques the surveillance state and the idea of a single individual acting as judge, jury, and executioner.

Near and Mello are L's successors from Wammy's House, an orphanage for gifted children. Introduced in the second half of the series, they represent two different aspects of L: Near possesses L's calm, analytical deduction, while Mello possesses L's drive and willingness to take action. Together (though often working separately), they continue the hunt for Kira after L.

While the main story of Light and L is complete, there have been follow-ups. The 'Death Note: Special One-Shot' (2020) features a new protagonist, Minoru Tanaka, who tries to sell the Death Note rather than use it. There are also light novels like 'Death Note: Another Note', which details a previous case L solved involving the 'Los Angeles BB Murder Cases'.

The ending of Death Note is tragic and complex. Without spoiling specific details, neither Light nor L achieves a total, unblemished victory. The series concludes by showing the ultimate consequences of playing god, reinforcing the idea that the power of the Death Note is a curse that brings misfortune to everyone who touches it.