Death Note - Season 1 (2006)

Evil people start dropping dead mysteriously after an intelligent high school student stumbles upon a shinigami’s death note

Ryuk, a bored Shinigami (god of death), decides to stir up some chaos by dropping his Death Note, a magical book that can be used to detail how and when you want somebody to die, into the human world. When Light Yagami, an intelligent high school student, comes upon the book, he uses it to rid the world of evil, assuming a god-like role in human society. As the deaths begin to spiral out of control, L, a masked detective, is assigned to hunt down the culprit behind the mass murders, kickstarting a tense and high-stakes cat-and-mouse game between the two geniuses.