Soichiro Yagami

Soichiro Yagami (夜神 総一郎, Yagami Sōichirō) is Light's father and a police officer that initially leads the Kira investigation team. He is voiced by Naoya Uchida in the Japanese anime and Chris Britton in the English dub. In the film, he is played by Takeshi Kaga.

Plot
As work on the Kira case begins, he becomes disappointed with the lack of police cooperation in capturing Kira, eventually joining forces with L to form a special investigative team. When L begins to suspect Light of being Kira, Soichiro is unwilling to believe his son would be capable of such a thing. Though he eventually suffers a stress related heart attack, he insists on remaining helpful to the team, going as far as breaking into the Sakura TV station using a police bus.

Much later, after L is killed and replaced by Light, he is instrumental in regaining the Death Note which Mello had pressured them into relinquishing by threatening Soichiro's daughter. Using Kira's Death Note, which Misa delivers to him under Light's instruction, Soichiro trades with Ryuk for the Shinigami Eyes. Using the eyes, he is able to learn Mello's real name, though he is fatally wounded by one of Mello's gang members and their bomb. Because Light has given up his Death Note and therefore his lifespan is visible, Soichiro dies happily believing that Light isn't Kira.

Live Film Adaptation
The second film departs significantly from the manga, in that Soichiro survives. L manages to expose Light as Kira, and the latter dies in Soichiro's arms begging him to believe that he acted as Kira to put justice into effect. A year later, on Light's birthday, Sayu fetches Soichiro from the train station, and claims he told her that Light was killed by Kira. While Soichiro wears glasses throughout the manga and anime, Takeshi Kaga only wears them briefly in the first film and as such, Kaga does not have a mustache. Also he makes a cameo apperience in Full Metal Panic: Second Raid, between Light and Misa.

Trivia

 * Soichiro died about 1 hour after eye's trade, so he was in fact fated to die 2 hours later.