Kojirō Ryūzaki is the president of the talent agency B-Dash, which manages the career of popular actor Ryouma Ichijou. He has maintained a longstanding professional and personal relationship with his secretary, Tenma Hidaka, and despite having a youthful appearance, he is notably older than he initially appears. His personality is defined by a strict and volatile temperament. He is quick to anger, often raising his voice and making contradictory statements during arguments. His frustration most visibly manifests in his habit of standing on top of his desk when enraged.

His primary motivation is the protection and advancement of his agency and the careers of its talents, which places him in direct opposition to anything he perceives as a threat to that stability. Within the story, he acts as a representative of the professional entertainment industry, imposing external pressure and conflict on the central romantic relationship. Upon suspecting that Ryouma is involved with Izumi Sena, who is associated with the rival agency SenaPro, he becomes furious. This opposition introduces a significant inter-agency rivalry that Ryouma must navigate between his personal feelings and his professional obligations.

Kojirō's key relationships are largely defined by his professional authority. He serves as the direct superior to Ryouma, actively supervising his career. He shares a long-term bond with his secretary Tenma Hidaka. Conversely, his allegiance to B-Dash naturally creates an antagonistic dynamic towards the Sena family and their agency, SenaPro. While he does not undergo a major personal transformation over the course of the narrative, he serves as a consistent obstacle representing the corporate side of show business. His notable abilities include the business acumen and executive authority required to run a competitive talent agency, allowing him to control casting decisions and career paths.