Soichiro Yagami is Light's father and a detective superintendent at Japan's National Police Agency—basically one of the top cops in the country. He heads up the task force hunting Kira in the early stages of the investigation, and later works alongside L when their efforts merge.
The thing is, Soichiro's parental instincts get in the way of his detective work. When L starts zeroing in on Light as a suspect, Soichiro flat-out refuses to believe his son could be Kira. He's convinced of Light's innocence, which clouds his judgment at some crucial moments. It's one of those tragic elements of the series—a good cop who can't see what's right in front of him because it's his own kid.
Content compiled by AnimeList.moe from publicly available sources.
