The core plot device of the story is the “Death Note” itself, a black notebook with instructions (known as “Rules of the Death Note”) written on the inside. When used correctly, it allows anyone to commit a murder, knowing only the victim’s name and face. According to the director of the live-action films, Shusuke Kaneko, “[t]he idea of spirits living in words is an ancient Japanese concept… In a way, it’s a very Japanese story”.
Artist Takeshi Obata originally thought of the books as “Something you would automatically think was a Death Note”. Deciding that this design would be cumbersome, he instead opted for a more accessible college notebook. Death Notes were originally conceived as changing based on time and location, resembling scrolls in ancient Japan, or the Old Testament in medieval Europe. However, this idea was never used.
Writer Tsugumi Ohba had no particular themes in mind for Death Note. When pushed, he suggested: “Humans will all eventually die and never come back to life, so let’s give it our all while we’re alive”. He went on to say that “no human has the right to pass judgment on another’s actions. No one should play God”. He said that Near‘s climactic speech about good and evil was rooted in his own beliefs.
In a 2012 paper, Jolyon Baraka Thomas characterised Death Note as heavily influenced by the conflicts between liberty and security; as illustrating that high moral ideals are easily corrupted, and that people will always justify horrific acts of violence in the name of safety. Thomas writes that “the price of peace is death”.
Thomas’ paper lists Death Note as one of the later and more sophisticated psychological thrillers released in the wake of the 1995 Tokyo subway sarin attack, saying that it examines the human tendency to express itself through “horrific” cults and describes the negative effects of those cults on the members, on their families, and on society. Through the moral relativity that characterizes the story throughout, readers are reminded that their own ideas of good and evil might not differ so much from those of extremist cult members.