Okita Sōji
Nobuhiro Watsuki has stated that the character design of Sōjirō is loosely based on Okita Sōji, the captain of the first Squad of the Shinsengumi. The name Seta Sōjirō originates from "Okita Sōjirō," the name Okita had in his early life. The specific personality model is from the Okita in Ryōtarō Shiba's novel "Shinsengumi Keppuroku" ("Record of Shinsengumi Bloodshed"); in that version Okita "lost an important part in his human heart," making him without emotions and "pretty scary." Watsuki reported that some fans did not like the fact that a character modeled on Okita is a villain; Watsuki argued that since Sōjirō is based on the "Shinsengumi Keppuroku" Okita, the design "works well" and that Sōjirō is "a strong antagonist." Watsuki felt that Sōjirō was more difficult to draw than Watsuki initially anticipated, and that he only accomplished around one fourth of what he imagined the character would appear in his mind. Watsuki had no design model for Sōjirō; Watsuki envisioned Okita as having bangs (fringes), so to Watsuki it was no surprise that Sōjirō also had bangs. Watsuki gave Sōjirō a "slightly feminized air" so that Sōjirō's smile would "look good" on the character. In Volume 9 Watsuki stated that he wants to properly portray Sōjirō since he is a popular character.