In the anime "Death Note," Light Yagami believes that his actions are justified because he sees himself as a savior who is purging the world of criminals. Truth plays a significant role in Light Yagami's plans as he manipulates and uses it to achieve his goal of creating a new world free of crime. He uses the Death Note to kill criminals and those who oppose him, all while trying to maintain a facade of righteousness to deceive both his allies and enemies. Ultimately, his obsession with truth and justice becomes distorted as he becomes consumed by power and the desire to control the world.