The character known as Astronaut with glasses from the film Kamen Rider: Hachi-nin Rider tai Ginga-oh is a supporting figure whose design and function are closely tied to the film's science fiction themes. He is typically depicted as a Japanese astronaut and scientist, identifiable by his standard astronaut attire complemented by a pair of glasses, which visually sets him apart from the action-oriented heroes and emphasizes his intellectual role.

His background establishes him as a dedicated researcher and space explorer, often involved in studying astronomical phenomena or advanced technologies. His glasses are not merely a cosmetic detail but serve as a visual shorthand for his analytical and methodical personality. He is portrayed as calm, brave, and principled, displaying a strong sense of duty to his work and a deep concern for the safety of Earth. His primary motivation is to protect his family and humanity from the cosmic threat posed by the villain, which drives him to take significant personal risks.

In the story, his role is primarily that of a victim and a motivator. He is often captured by the antagonist, Ginga-oh, who needs the astronaut's expertise or a specific component of his space station to power his doomsday plans. His capture serves as the catalyst for the Kamen Riders to spring into action. Rather than being a fighter, his function is to provide the heroes with critical scientific information about the villain's weaknesses or to be the person they are racing against time to rescue. Key relationships include his bond with his daughter or a younger colleague, whose emotional pleas for his rescue add a personal stake to the larger cosmic battle.

In terms of development, the character undergoes a transition from a helpless captive to an active participant in his own rescue. While he may not gain superhuman abilities, he demonstrates resourcefulness and courage, potentially sabotaging the villain's equipment or relaying vital intelligence from inside the enemy base. His notable abilities are not combative but intellectual, including expertise in astrophysics, piloting spacecraft, and operating complex machinery. His resilience under pressure and his willingness to sacrifice his own safety to help the Riders ultimately prove as valuable as any physical power, reinforcing the theme that heroism takes many forms.