A shinigami, as a god of death, can kill any person—provided they see their victim's face and write their victim's name in a notebook called a Death Note. One day, Ryuk, bored by the shinigami lifestyle and interested in seeing how a human would use a Death Note, drops one into the human realm. High school student and prodigy Light Yagami stumbles upon the Death Note and—since he deplores the state of the world—tests the deadly notebook by writing a criminal's name in it. When the criminal dies immediately following his experiment with the Death Note, Light is greatly surprised and quickly recognizes how devastating the power that has fallen into his hands could be. With this divine capability, Light decides to extinguish all criminals in order to build a new world where crime does not exist and people worship him as a god. Police, however, quickly discover that a serial killer is targeting criminals and, consequently, try to apprehend the culprit. To do this, the Japanese investigators count on the assistance of the best detective in the world: a young and eccentric man known only by the name of L. 名門大学に通い、将来の警視総監を嘱望される天才・夜神月(やがみライト)。 彼は偶然手に入れた、名前を書かれた人は死んでしまうノート"デスノート"を使い、法で裁かれない犯罪者を次々と殺していく。 その目的は犯罪のない理想社会の実現だ。 一方ICPO(インターポール)は犯罪者の大量死を殺人事件と考え捜査を開始。 世界中の迷宮入り事件を解決してきた謎の探偵・Lを捜査に送り込んできた。 そして月とL、2人の天才による壮絶な戦いが始まるのだった。
