“I have a responsibility as a parent and as the chief of police.”
Soichiro wears a pair of rectangular spectacles at most times and is a fairly tall man. His appearance fits that of a middle aged man, and he prefers to dress in formal Western clothing.
Soichiro is a kind man with a strong sense of justice. He cares greatly for his family and the members of the Japanese Task Force. He is a serious and responsible man that gains the respect of many. He has a strong sense of duty, and even after the police stop funding the Kira investigation he continues trying to solve the case with the Task Force.
Throughout the Kira investigation he believes that his son, Light Yagami is innocent. In order to prove it he goes as far as to kidnap Light (who had given up the Death Note and lost his memories of ever using it) and his girlfriend, Misa Amane (who had also given up her Death Note and had no memories of it), and put them in a situation in which if Light were Kira, Light would have no choice but to kill him.
When his daughter Sayu is kidnapped by the Mafia, he becomes conflicted over whether or not he should follow their wishes and trade the Death Note for Sayu. His dilemma comes from having to choose between the duty of an officer, and the duty of a parent. As a police officer and the Chief of the NPA, he believes that handing over the Death Note to the Mafia is wrong, and the Death Note in the hands of the Mafia is too great a risk. However, he ultimately decides that he will make the exchange, not as an officer, but as Sayu Yagami's father.
As work on the Kira case begins, Soichiro becomes disappointed with the lack of police cooperation in capturing Kira, eventually joining forces with L to form a special investigative team. When Ryuzaki 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 Ryuzaki is killed and replaced by Light, Soichiro is instrumental in regaining the Death Note, which Mello had pressured them into relinquishing by kidnapping Soichiro's daughter Sayu. Using Kira's Death Note, which Misa delivers to him under Light's instruction, Soichiro makes the Shinigami Eye Deal with Ryuk, allowing him to gain the Shinigami Eyes. Using the eyes, he is able to learn Mello's real name, though he is fatally wounded by Jose, one of Mello's gang members, and their bomb. Because Light has given up his Death Note to make his lifespan is visible while keeping one on him to prevent his memories from being erased, Soichiro dies happily believing that Light is not Kira. The rest of the Task Force, consisting of Shuichi Aizawa, Touta Matsuda, and Hideki Ide, continues to respect his wish to the very end in the pursuit of Kira.
His death later plays a major role in the Kira's defeat when Light is exposed in front of Near, the SPK, and the Task Force, resulting in Matsuda, who was enraged at the fact that Light was the one who drove his father to death in a cold-blooded fashion, shooting him multiple times to prevent him from using the Death Note.
In other media
Soichiro's role in the film series is essentially the same, although Death Note: The Last Name departs significantly from the manga. Ryuzaki manages to expose Light as Kira in front of the entire Task Force including Soichiro, and Soichiro saw Light's attempt to write down his father's name. Light tries to convince Ryuk to write down the names of the Task Force members, and Ryuk writes down Light's name. Light dies in Soichiro's arms begging him to believe that he acted as Kira for the sake of justice.
In the Matsuda short film, Matsuda is having trouble getting closure in the case. Soichiro gets a note to Matsuda for him to visit Ryuzaki, and Matsuda does so. In the main films, Soichiro visits L shortly before his death to report on the end of the case, and L apologizes for failing to save Light. Soichiro salutes him on his way out. A year later, on Light's birthday, Sayu fetches Soichiro from the train station, and she believes the story he told her that Light was killed by Kira.
Soichiro's role in Death Note: The Musical is generally the same as in other adaptations, although the Musical has some changes to the story. After receiving the reports of criminals dying, Soichiro makes the call to bring in L to assist on the case. He is openly disapproving of L's extreme methods. L sacrificing Lind L. Tailor crosses a line for him, which he discusses with Light. When Misa is apprehended, he calls L out on her treatment directly. However, Soichiro comes to realize that Light is Kira. He survives his son and silently mourns for him in the final song.
Takeshi Kaga, who plays the character in the films, reprised his role for the 2015 Japanese production. Tetsuya Bessho (別所哲也) will portray the character in the 2017 Japanese production. Lee Jong-Moon (이종문) portrayed the character in the 2015 Korean production, and Seo Young-Ju (서영주) portrayed the character in the 2017 Korean production.
Soichiro performs the following songs:
- Don't Cross That Line is the song Soichiro sings about his disapproval of L's methods regarding his sacrifice of Lind L Tailor to find Kira. Light joins in to the song briefly as well.
- Secrets and Lies is an ensemble song with L and Light about the progress of the case.
- Honor Bound is the song Soichiro sings when he begins to accept that Light might be Kira.
Soichiro's role in the television drama is generally the same as in other adaptations, although the story has major changes to the plot.
Prior to the beginning of the series, Soichiro is out working a case and does not make it to the hospital when his wife's condition worsens. Sachiko Yagami dies in the hospital, with Light and Sayu alone with her. This causes a rift between Light and his father, and Light loses his dream of becoming a police officer.
At the beginning of the series, Soichiro trades himself for a hostage and is held at gunpoint. This prompts Light to intentionally kill the criminal with the Death Note to save his father's life, which leads Light to realize that the notebook can be used for justice. This event is one of the reasons that L suspects Light, and when L points it out to Soichiro, Soichiro begins to suspect his son as well.
Soichiro definitively discovers that Light is Kira when he comes across Light shortly after Light retrieves the Death Note that was taken by Mello and Shoko Himura. Light lies and says the Death Note isn't real, but Soichiro knows it is and writes his name into the notebook, perhaps in part to see if Light would stop him or let him die. He then tries to set it on fire, but Light fights him for it much more aggressively than he tried to stop Soichiro from writing his name, showing how far Light's become devoted to Kira over his family. Soichiro dies of a heart attack before he is able to successfully burn the notebook, and Light pries the notebook out of his dead father's hand.
Yutaka Matsushige portrays Soichiro in the television drama.
- “Only those who are ready and willing to sacrifice everything and fight, who are truly committed to stopping this psychopath… are asked to remain. I'll find out who you are when I return at five o'clock from my meeting upstairs.” (Chapter 10)
- “Kira is evil, there’s no denying that. But lately I've been starting to think of it more like this. The real evil is the power to kill people. Someone who finds himself with that power is cursed. No matter how you use it, anything obtained by killing people can never bring true happiness.” (Chapter 22)
- “I'm sorry, Sachiko.” (Chapter 67)
- “Light... I trust you.” (Chapter 72)
- “I...I'm sorry... I couldn't kill him after all.” (Episode 29)
- “I will not succumb to evil.”
- “Light was murdered by Kira…” (L: Change the WorLd, p 185)
- “Ryuzaki… you're back.” (L: Change the WorLd, p 186)