Birthdate: February 28, 1986 (1989 in the anime)
Zodiac sign: Pisces
Hair color: Brown
Eye color: Brown
Height: 179 cm (5'10")
Weight: 64.1 kg (141 lbs.)
Blood type: A
Occupation: high school student, a university student, detective
Age (during the series): 17-23
Likes: Justice
Dislikes: Evil

Light, born on February 28, 1986, is a third-year high school student (12th grade) at Daikoku Private Academy (大国学園, Daikoku Gakuen) who also attends supplemental classes at Gamou Prep Academy at the beginning of the story. Light has a father, Soichiro Yagami, who is the head of the Police Force. Light also has a mother, Sachiko Yagami, and a younger sister, Sayu Yagami.

In Spring 2004, Light becomes a first-year student (freshman) at To-Oh University (東応大学, Tōō Daigaku), becoming one of two freshman representatives; L is the other freshman representative. During a tennis game with L at To-Oh, spectators reveal that Light was the junior high school tennis champion in 1999 and 2000. After his 2000 victory, Light quit tennis as he entered high school.

Yagami Light is a brilliant college student. Nicknamed "Kira," he uses the Death Note to create his ideal world of justice under him, its new God. Though he looks frail, Light is an extremely athletic person, with an aptitude to find an opponent's weak point. He is a genius, which adds to his notion that only he is fit to judge humanity and steer it on a proper moral course.