The hit series Death Note follows protagonist Light Yagami, who obtains a magical notebook that kills anyone by simply writing their name in it. The series is filled with social commentary as Light begins killing criminals to create a modern-day utopia, and the titular Death Note is described as the most dangerous weapon on Earth. This draws a parallel to another powerful weapon, one that has blasted its way through both Japanese consciousness and the entire anime genre: the nuclear bomb.
Admittedly, this might seem like a bit of a stretch to some. However, there are several clues that suggest the Death Note serves as a metaphor for the atomic bomb, especially if the series is examined in the context of surrounding events.
The first third of the story deals with Light's acquisition of the Death Note from the shinigami Ryuk. He begins targeting criminals and exploring the limits of what the notebook is capable of, and is dubbed "Kira" by the media. Meanwhile, another young man nicknamed L is hired to help the police track down Kira. Eventually Light begins working alongside L and a special police task force to determine Kira's true identity, even as L openly admits that Light is the primary suspect. After L is killed, the final third of the series explores a world that has been completely altered by the presence of Kira. Light has become the leader of the anti-Kira task force, killing more and more innocent people to protect his identity, transforming himself from a vengeful anti-hero into a relentless mass murderer without scruples.
The entirety of Death Note explores political themes relating to the criminal justice system, the media, and international policy, but it is the final third where the politics become particularly blatant. All wars cease. Global crime rates drop by 70%. Eventually, the US President issues a statement declaring his government will not work against Kira. Meanwhile, L has left two successors, nicknamed Melon and Near, who figure out that Light really is Kira and work to stop him. In the final episode, Near condemns Light/Kira as a murderer and calls the notebook "the deadliest weapon in the history of mankind." This statement is not subtle. It is directly comparing the Death Note to the atomic bomb.
The specter of the nuclear war is burned into the Japanese consciousness and is an integral part of anime. Classics works like Akira, Grave of the Fireflies, and Astro Boy deal with the traumatic legacy of nuclear terror. To this day, survivors of Nagasaki and Hiroshima have a special place in Japanese society, being referred to as Hibakusha. But over the decades, the political landscape has shifted.
Death Note deals with modern political issues. While the main ongoing series ended in 2006, a great example of its politics is depicted in 2020's Death Note: Special One-Shot, in which then-US President Donald Trump claims to have acquired a Death Note. He does not actually have one, but the mere belief that he possesses such a weapon allows him to push his own political agenda onto the rest of the globe.
This updated nuclear metaphor is not one of devastation and surviving in the aftermath, but of a weapon as a coercive tool used to threaten others. Between 1945 and 1949, the United States was the only country with an atomic bomb. They used the threat of nuclear annihilation to enforce their own agenda after World War II. General MacArthur oversaw the rewriting of the Japanese Constitution. This is similar to how Light/Kira is originally the only person in possession of a Death Note, which he uses to reshape global politics.
Junichiro Koizumi was Prime Minister of Japan from 2001 through 2006, stepping down the same year the Death Note manga finished and the anime was released. As the leader of Japan's right-wing Liberal Democratic Party, Koizumi was criticized by many Japanese people for supporting war criminals and committing troops to fight in Iraq at the urging of US President George W. Bush (though Bush put less pressure on Koizumi than he did on other foreign leaders).
This shows how US militarism's influence on Japanese politics continues to the present. Death Note deals with the politics contemporary to its own time by inverting this power dynamic -- as Kira (and by extension Japan) is in possession of the ultimate weapon. It does not matter who Kira actually intends to kill, so long as world leaders know he has the power to destroy them. In this vein, the nuclear metaphor of the Death Note is not one of a bomb exploding, as the mere threat of such a weapon is enough.