Hideki Shibuya is a resident of the southern island that serves as the primary setting for Star Driver. He is known locally as the town's doctor and the owner of its hospital, a position that gives him a respectable standing in the community. His physical appearance is that of a mature man with gray hair, often seen wearing glasses and a lab coat, fitting his professional role as a physician and scientist. However, this public identity masks his secret affiliation with the Glittering Crux Brigade, a mysterious organization operating on the island. Within this group, he is known by the code name Professor Silver and is a key member of its Science Guild.

As a scientist, Shibuya is depicted as an individual of significant intelligence whose expertise lies at the intersection of medicine and the advanced, ancient technology known as Cybodies. His scientific contributions are central to the Brigade's operations. Together with a colleague known as Professor Green, he is credited with constructing much of the equipment necessary for piloting Cybodies. This includes the development of the Cybercaskets, which are the specialized devices that allow a Driver to interface with a Cybody. His research also unlocked the formula for Cybody regeneration, a vital capability for the organization's ongoing experiments and power struggles.

One of his most notable solo achievements is the invention of the Overphase System. This machine is designed to artificially amplify the connection, or phase, between a Driver and their Cybody, thereby increasing its power output. This technology represents a significant advancement in the Brigade's goal of harnessing the full potential of the giant robots, as it allows for a temporary boost in strength that might not otherwise be naturally achievable. His technical prowess is further underscored by his long-standing role as the personal physician to Shingo Makiba, a key figure who remained in a coma for seventeen years, indicating a deep and enduring involvement with the consequences of Cybody usage.

Regarding his motivations and role within the story's conflict, Shibuya's loyalties are not entirely straightforward. While he operates under the leadership of Professor Green, the head of the Science Guild, Green herself is known to address him with polite and respectful language, suggesting a complex dynamic where his expertise is highly valued. More critically, he is revealed to have been in secret communication with Vanishing Age, a specific faction within the larger Glittering Crux Brigade. His involvement with them culminates in his complicity in their attempted coup d'état during the latter half of the story. This act of betrayal against the main organization highlights a character whose primary loyalty may not be to the Brigade's leadership, but to his own long-term research or personal convictions, which may align with the goals of Vanishing Age.

His key relationships are thus defined by a dual existence. As a doctor, he is a caregiver to figures like Shingo Makiba, maintaining a professional and personal duty of care. As Professor Silver, he is an indispensable technical asset to the Glittering Crux Brigade, yet his secret dealings reveal him to be an internal political player willing to switch allegiances to further his own agenda. Throughout the narrative, Hideki Shibuya embodies the archetype of the morally ambiguous scientist, whose considerable abilities in medicine and robotics make him a powerful, albeit quietly treacherous, force behind the scenes. His development is marked not by a change in personality but by the revelation of his secret machinations, exposing the deep-seated conspiracies that drive the central conflict.