Kensuke Tachibana holds a managerial position within the Oohara yakuza family. As the younger brother of Naoki Satoya's mother, he is Naoki's maternal uncle. Kensuke relentlessly pressures Ryuunosuke Oohara, the reluctant heir, to accept his destined role as the fifth leader ("Fifth") of the organization. To achieve this, he approaches his nephew Naoki, leveraging their childhood friendship to urge Naoki to convince Ryuunosuke to succeed his father. Kensuke emphasizes that Ryuunosuke need not assume leadership immediately, proposing a formal takeover approximately two months after Ryuunosuke's high school graduation, timed with the fourth leader's declining health.

Kensuke fundamentally misunderstands the nature of Ryuunosuke and Naoki's relationship, incorrectly believing their commitment is solely tied to the gang's succession. This misconception fuels his dismissal of their personal concerns about maintaining their bond if Ryuunosuke becomes Oyabun. His actions throughout the narrative are driven by a persistent focus on securing the gang's future stability.

Physically, Kensuke is depicted with sleek hair, a facial scar, and is often seen wearing a vest. His role remains strictly managerial, with personal backstory and character development limited strictly to his function as an antagonist opposing the protagonists' goals. No further narrative expansion or development occurs for this character in official sequels or related media.