Death Note: Return from Purgatory is a fanfiction written by DemonsAnarchy, set immediately after the death of Light Yagami. It is essentially a story of how Light retrned to the day when everything began with the power to change everything, including himself. However, his new life has a catch: if he dies, his soul will be devoured.
After Light dies, he awakens in his bedroom, initially believing that the events of the anime were nothing but a dream, but he is vastly disturbed by his dream self's actions as Kira, and believes that nothing good could come from being a sociapath. However, upon discovering the Death Note once again, he grows horrified, and refused to become Kira. It isn't until he sees the news that a man is about to kill someone that he uses the Death Note, thus sealing his fate.
However, just after this, he meets a mysterious being named Hades, who calls himself the King of the Shinigami, thus making him the ruler of the Shinigami World. He states that he took Light from Mu and returned him to the day in which he first became Kira under the pretext that he was bored, however he also asks Light if he still has the intention of becoming a God of a new world order filled with honest, kind, and hard working people. Before Light gives his decision, Hades warns him that, should he die this time, he will devour his soul. However, Light states that he is no longer the arrogant murderer he used to be, stating that he will be the judge of humanity's sins. With that in mind, Light once again takes up his role as Kira, and resumes his quest to bring about a new world order.
The protagonist of the anime/manga series, as well as the messiah-like figure "Kira". Light is what one could consider a prodigy, standing at the top of his classes, always studying, however he is vastly disturbed by the works of society, seeing the lack of justice being carried out. In the original timeline, Light used the Death Note to become a god-like figure that watches over a world filled with honest, kind, and hard-working individuals while also killing those that stood against him in his pursuit to create such a world. However, in the story, he is no longer arrogant, thinking himself to be akin to that of a judge that weighs humanity's sins on a scale, and unlike his previous self, he relishes the battle of wits between him and L, stating that he rather missed it, giving out hints about the Death Note and even his identity as Kira every now and then.
L is the world's most formidible detective, though his appearance is very lacking. He was brought into the Kira investigation case when he learned about the unique method of the murders being carried out. In the original timeline, he and Light were at odds with each other, but overtime, they became good friends. In the story, L is baffled by Kira's actions, wondering why he would give his opponent hints about himself, as he originally thought that Kira was a being that aspired to be a God-like figure. Instead, however, Kira stated in a broadcast after the death of Lind L. Tailor that he already knew that he was a Death Row inmate scheduled for execution, and outright encouraged the police to catch him, considering the battle of wits to be a game to see who could create a world of justice and peace. The friendship between L and Light is already prominent in the beginning when they meet, unlike the anime.
"I'm not as arrogant as I was back then... I realize now that someone who believes themself to be a God is nothing but a child throwing a tantrum... No, what I need to become... What I must be... is a Judge. A judge of humanity's sins!" -Light Yagami
"I do not consider myself righteous. I do not consider myself a God. I do not consider myself a murderer. I am the one who weighs man on the scales of justice, and finds them wanting... You who side with the law, try to find me! We'll see who can create a world of justice and peace first! You, or me! I am Kira, and I am the Judge of Humanity's Sins!" -Kira's Rebirth
"Hm, I seemed to have been mistaken about Kira... He's no ordinary person. I may have to put a bit of effort into this case." -L
- Unlike the anime, Light allows the FBI agents to live, having seen what sort of hellish existence Kira's actions in the previous timeline brought in the past.