"Look around you, and all you see are people the world would be better off without"
- Light Yagami
About
Light is characterized as hardworking, talented, and a natural genius.
He is frustrated by the lack of justice in the world. Believing the world to be "rotten," he uses his Death Note as a means by which he can enact his will to rid the world of evil people. Light's main goal is to create a new world that is free of injustice and populated only with honest and kind people, thus becoming the "God of the new world". Light is decisive and driven to achieve his ambitions, without faltering one bit in his beliefs. Despite staining his hands with the blood of the people that he's killed, this extreme action can be said as a result of his unmoving resolve.
Through use of the Death Note, Light quickly begins to develop a cold, ruthless, and malevolent nature. He becomes completely devoid of love, compassion, and mercy. He views himself as the only rightful savior of mankind and that all his actions are justified, no matter how inhuman they might be. He is shown to even be willing to sacrifice his own family, if pushed to that point. The fact that he is intelligent also adds to his notion that only he is fit to judge humanity and steer it on a proper moral course.
Throughout the series, Light is constantly trying to evade the suspicion of L and other detectives while both maintaining his identity as "Kira"—the name derived from the Japanese pronunciation of the English word "killer" and cleansing the world of crime.
The Story
Light Yagami was a star student in his high school class. He was far more intelligent than other students and naturally graduated Valedictorian. He knew just about everything that there was to know and often scored higher than the rest of his classmates. He was able to stay popular among his peers despite keeping to himself most of the time.
He was sitting in class at the end of school one day at the end of his last period, bored. He never paid attention to the teacher and always stared out the window, bored. The teacher rarely called on him anyway, so why should he bother? He didn't care. As long as his mother was proud of him...maybe, maybe he might just try. He was a different kind of kid. He was extremely intelligent for being such a couch potato, but he never once even thought about exerting himself for anything other than exams.
"Mr. Yagami. Mr. Yagami! Answer the question please." the teacher said, looking at his daydreaming star student. Light then proceeded to answer the question with ease. Simple Calculus, he thought. He never understood why people thought it was so difficult. It was just numbers, and that was all. Just numbers.
He continued his daydreaming once more, and stared out the window, waiting for something. But, he didn't know what. He waited and waited, and still, nothing. What was this feeling of anxiety? He didn't know...but he didn't care. He suddenly saw something fall out of the sky and onto the grass outside. It was black and square shaped, and it looked different from other notebooks.
"Hmph...probably seniors at it again...tossing stuff off the building." he said under his breath. He mumbled a lot. He went outside after class and waited for the majority of his class to leave. He was curious about this book. He picked it up and looked at the black covered binding. On the cover it said "Death Note". Little did he know, this book would change his life and death as he knew it.
The Death Note is a notebook that has huge amounts of power. Using it the owner can write down any name he wishes and as long as he knows the face of the indivual then they will die withen 40 seconds. Throughout the series the rules where constantly being aired between breaks and are as follows.
-The human whose name is written in this note shall die.
-This note will not take effect unless the writer has the subject's face in their mind when writing his/her name. Therefore, people sharing the same name will not be affected.
-If the cause of death is written within 40 seconds of writing the subject's name, it will happen.
-If the cause of death is not specified, the subject will simply die of a heart attack.
-After writing the cause of death, the details of the death should be written in the next 6 minutes and 40 seconds (400 seconds)
However it also comes to be known that there are two other real rules, those above being the only ones listed in the notebook. the other two rules are as follows
-The human who uses this book , for personal gain or not, will not be allowed to go to either heaven or hell, but will spend three years in perpetual darkness then put into a state of limbo on Earth trapped for an eternity niether seen or heard by the living.
-You may also make an exchange half your life with the shinigami who has dropped the book for what are called shinigami eyes which allows the user to see the names and life spans upon looking at their face.
The shinigamis (also known as a death gods) are the original owners of the notebooks. If they do drop a notebook down to earth (weather out of boredom or by accident) they are bound to the human under which the notebooks ownership has been transfered to. In lights case the shinigami's name is Ryuk, the same shinigami in fact who had written he basic rules of the death note.
As stated above the story does start out with Light Yagami (kira) finding the notebook, but throughout the rest of the pages he begins to test it's limits relentlessly looking for new ways to utilize its powers for what he believes to be the beterment of man kind. However, in the police's point of view this is not the vision of the perfect world but rather the introduction to chaos. The Greatest detective in the world, only to be known as L or Ryuzaki throughout most of the series decides to enter himself into the investigation of the Kira Case. Unbeknownst to most, however, Light Yagami is actually the son of Chief of Police, who is co-leader of the Kira Case, which then gives Light the upper hand on as to what to expect. Light discovers L was suspecting that Kira may be a student based on the victims times of death. Light then uses this to his advantage. He deliberately shows L that he has access to police information so that L would suspect a cop of being Kira and thus start turmoil in the investigation. L deduces that Kira is a family member of someone in the Kira Taskforce, L bans people from talking about the Kira case at home and places many families under FBI surveillance, light noticing this begins his battle with L, in what is to be one of the greatest tactical story in this writers opinion to ever be published.
The battle starts with installation of cameras and wire taps in Light Yagami's home, Light conducts himself accordingly. Hiding a T.V. in a bag of chips as well as hiding the death note under another notebook and pretending that he is having a snack while doing his homework. Then one day while he was outside with Ryuk (his personal shinigami) alerted Light to the fact that he was being followed. at this point Light devised an elaborate plan to kill the man who was following him.
As a result of killing Ray Penber, the FBI agent assigned to follow him, Light would soon be forced to kill Penber's fiancee, Naomi. This helped L narrow down the possible Kira suspects to who Ray Penber had been following. With the appearance of the second Kira, Misa Amane, L asked Light to join him in his search for Kira. Light agreed.
Misa and Light would meet soon after, and Light chose to take advantage of Misa's obvious devotion to him. Unfortunately for them, L discovered evidence that Misa is the second Kira, and arrested her. Light knew it was only a matter of time before he too was arrested, so he devised yet another elaborate plan, and turned himself in.
His plan involved Ryuk creating a fake rule that said the user of the Death Note would die within thirteen days in the event of discontinued use. Light and Misa willingly gave up their memories of the Death Note, and Rem took one notebook away to be used by a new Kira. When the deaths started up again, and with Light and Misa's honest conviction that they were innocent, L had no choice but release them from their prisons, although he didn't free them entirely. Light and Misa would help L track down the new Kira, but once Light touched the Death Note, his memories came back. The fake rule created by Ryuk cleared Light and Misa of guilt, and they were both freed.
Light's plan to use Rem's love for Misa to kill L came through. Rem realized that with Misa once again using the Death Note, it wouldn't take long for L to catch her and sentence her to death. To save Misa, Rem wrote L's name in her Death Note, killing herself in the process. Light had won the battle against L.
With L now dead, Light would take on the role of L himself and continue the Kira investigation.
However, he gets two new opponents to fight: Near and Mello, the candidates for being L's successor. His fight with them leads Light to his defeat and also his death by the hands of Ryuk.
Death
At the age of 23, Light joins the Japanese Police Force's Intelligence Department in order to have better access to police information.
Near and Mello, the "true successors of L" eventually appear before him, trying to accomplish what L could not: exposing Kira's true identity and bringing him to justice. Near joins the Special Provision for Kira (or the SPK) for help in his endeavor, and Mello decides to use the Mafia for his investigation. Because of Mello's unscrupulous, criminal methods, Near sides with Light, not knowing that the latter is Kira. Mello is able to at one point take the notebook away from Light, but the combined efforts of Light and Near allow Light to regain the notebook at the cost of his own father's life (which Light would later explain to have been a necessary sacrifice).
Once Near realizes that Light was responsible for the lack of progress in the case as the new L, he begins to suspect that Light may in fact be Kira. With a prosecutor named Teru Mikami acting as a new proxy, Light formulates a plan to eliminate not only Near but the surviving members of the Task Force and the SPK as well. Near, likewise, forms his own plan to finally expose Light as Kira. However, Mello intervenes and manages to cause Mikami to make a mistake, smashing Light's plans into the dust.
Light, Mikami, the SPK and the Task Force all eventually meet at the Yellow Box warehouse, where Near uses Mikami to expose Light as Kira. After confessing and attempting to justify his actions to the people tasked with capturing him, Light tries to kill Near with the notebook clipping hidden in his watch, only to be shot by Touta Matsuda, a member of the Task Force.
Mikami commits suicide by stabbing himself with his pen and losing a lot of blood, creating a diversion for both the Task Force and the SPK. Although weakened, Light catches a second wind and manages to flee the warehouse. Near tells Aizawa, Mogi, Ide, and Matsuda that there is no reason to pursue Light given that there should be no more hidden Death Note pieces and Light's wounds would prevent him from getting far. Aizawa refuses to heed Near's orders and has his team follow Light. Meanwhile, Ryuk writes Light's name down when the latter finds another warehouse to hide in. As Light silently dies, an illusion of L appears before Light, mirroring a scene following L's defeat at Light's hands
Here's a quick recap of that old nostalgia :-