Soichiro Yagami (夜神 総一郎, Yagami Sōichirō) is Light's father and a police officer that initially leads the Kira investigation team that later joins with L. He is voiced by Naoya Uchida in the Japanese anime and Chris Britton in the English dub. When L begins to suspect Light of being Kira, Soichiro is unwilling to believe his son would be capable of such a thing. After L's death, he is sent to retrieve the Death Note stolen by Mello by obtaining Shinigami Eyes and infiltrate Mello's hideout, though Light had planned for Matsuda to fill the role. He retrieves the note and learns Mello's real name, but is unable to kill him, and is instead fatally wounded. Because Light has given up his Death Note, making his lifespan visible above his head, Soichiro dies believing that Light is not Kira. In the film, Soichiro, portrayed by Takeshi Kaga, survives- discovering that Light is Kira and holding him as he dies- but chooses to hide the knowledge from his family.
Soichiro was envisioned as an "honest police officer with a strong sense of justice" that the reader "would have to feel sorry for everything he has to go through." Though Ohba did not want Soichiro to die, the writer felt that he had to because the character's continued existence would have interfered with too many of the already set up plot points. He did not want Light to kill him, so he wrote Soichiro's death as an accident. Obata designed Soichiro to look like a "stereotypical detective", retaining the mustache and glasses found in Ohba's concepts. Over the course of the series, he changes visibly by losing weight and aging poorly- particularly during his and Light's confinement. Both Ohba and Obata found Soichiro to be the most pure character, and Ohba personally found him to be the third strongest character in the series "besides Light." His birthday is July 12, 1955 (1958 in the anime).