小池一夫
Writer Kazuo Koike stated in an interview that he crafted the comic to be based upon the characters themselves and that the "essential tension between [Ittō's] imperative to meet these challenges while keeping his son with him on the journey" drove the story. According to Koike, "Having two characters as foils of each other is what sets things in motion" and that "If you have a strong character, the storyline will develop naturally, on its own."