He is a young man, standing at above average height with light brown hair and brown eyes. He tends to dress very neatly and formally, often seen wearing his school uniform or a suit. He is considered to be quite handsome, a trait noted by Misa Amane and Kiyomi Takada, among others.
Light is characterized as hardworking, talented, and a natural genius. Light would constantly predict all of the possible scenarios that could happen, and plan a solution in advance, even in the most impromptu situations. His only faults are his deep sociopathic interior, his cynical outlook on life, his overconfidence in himself and in his belief that he is never wrong.
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. Then, he will become the "God of the new world".
Light is decisive and is 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 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 to further his goals.
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" (キラー, kirā)—and cleansing the world of crime. 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.