Jinnai Shogo is a character from the anime and light novel series Black Blood Brothers. He holds the position of head of the Coordination Department for the Order Coffin Company, an organization that deals with vampire-related affairs. Unlike many of the series' key figures, Jinnai is entirely human, a fact that defines his role and his legacy within the story's world. He is recognized as the first person in the world to successfully mediate between humans and vampires, a groundbreaking achievement that allowed for a tenuous but functional coexistence. This skill culminated in his leadership in establishing the miraculous human-vampire united front during the conflict known as the Hong Kong Temple incident. As a result of his actions there, he is regarded as a hero of the holy war and is one of the few individuals, and the only human, whom the great vampire Jaja acknowledges as a worthy rival.

Jinnai's appearance is that of an adult male with short black hair and black eyes, typically dressed in a suit and tie that reflects his professional role within a formal organization. His true significance, however, lies in his profound connections to the central characters and the hidden history of the vampire world. He is a former comrade-in-arms of Jiro Mochizuki, the protagonist and a legendary vampire known as the Silver Blade. Their bond is built on shared experience and trust forged in battle, making Jinnai one of the few humans Jiro respects. Furthermore, Jinnai is the only human who knows the precise location where King Kuron, the progenitor of the Kowloon Children, is buried. This knowledge places him at the center of the story's conflict and makes him a target for those who seek to revive or exploit the King's power. He is also the guardian who raised Mimiko, a young girl who serves as a mediator between the human and vampire worlds, thus acting as a father figure who trains and protects her.

The character's motivations are rooted in pragmatism and a desire for a sustainable peace. He works to maintain the fragile balance between species, and his role in the story often involves strategic planning and direct intervention to prevent the collapse of that order. Jinnai is not a fighter of supernatural ability, but his bravery and tactical mind are his primary weapons. A key example of this is his final confrontation with Lau, the eighth of the powerful Kowloon Children, at a location known as Eleven Yard, where King Kuron's regrets are sealed. Despite being a human facing a vastly superior vampire, Jinnai engages in a bloody battle and succeeds in stopping Lau, securing a crucial victory at the cost of his own life. After his death, the Dragon King of the East, known as Sei, who respected Jinnai's strength and will, offered to turn him into a vampire to save him. This act would have incorporated Jinnai into Sei's own bloodline, granting him immortality and power. However, Jinnai refused the offer. His decision to reject eternal life as a vampire and accept death as a human underscores his fundamental nature and beliefs. He chose to end his existence on his own terms as a mortal, solidifying his identity as a person who valued his humanity above all else. His development thus moves from a skilled coordinator to a decisive, self-sacrificing hero whose ultimate act is a declaration of his human spirit.