In "Death Note," the theme of the fine line between justice and vengeance is explored through the characters of Light Yagami and L, who represent different perspectives on this theme. Light initially believes he is bringing justice by using the Death Note to eliminate criminals, but as his actions become more extreme, it becomes clear that his pursuit of justice is fueled by a desire for vengeance against those he deems as evil. On the other hand, L, the detective chasing Light, represents a more traditional view of justice, seeking to uphold the law and prevent unnecessary deaths, even if it means apprehending Light at all costs. The series raises questions about the morality of seeking justice through extreme means and the blurred lines between seeking justice and seeking revenge.