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 purest character, and Ohba personally found him to be the third strongest character in the series "besides Light." His birthday is July 12, 1955.