If we catch Kira, he is evil, If he wins and rules the world then he is justice
Light Yagami (夜神月, Yagami Raito) is the main protagonist of the Death Note series. After discovering the Death Note, he decides to use it to rid the world of criminals. His killings are eventually labelled by people of Japan as the work of "Kira."
Light is a young man, standing at above average height with light-brown hair and brown eyes. During Part I, when not wearing his school uniform, which consists of a tan suit and red tie, he dresses fairly casually, sometimes sporting a dress shirt underneath a jacket or a V-neck sweater with a collared t-shirt underneath. During Part II, if not wearing a similar style of clothes, he is seen wearing 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. Highly perceptive and good with problem solving, Light was a skilled planner and good at mapping out scenarios. Furthermore, Light was very popular among peers and adored by his family members. However, his high intelligence and constant praise from adults laid the foundation for an intense level of hubris which quickly took effect once he obtained the notebook.