Shigeru Satō stands among the trio of Egaogaoka Middle School boys who observe and comment on the magical girl team, Prima Angels, rather than joining their battles against the Darkness Whales organization. He shares classes and observations with friends Kiyoshi Suzuki and Isamu Takahashi.

Visually, Shigeru wears glasses and possesses distinct yellow eyes. Sources present his hair as either black or brown. His typical attire features yellow clothing, and he is frequently seen wearing headphones.

Personality-wise, Shigeru serves as the acknowledged "brains" of his friend group. He maintains the deepest knowledge of Prima Angel lore and Darkness Whales activities, gained through diligent, focused research, primarily scouring online forums. Outwardly, he often appears quiet, collected, and somewhat dazed or detached. Despite this reserved demeanor, he holds a deep enthusiasm for the magical girl phenomena. This passion occasionally surfaces when he surprises his friends with unexpectedly detailed explanations of events, concepts, or threats related to the Prima Angels' actions. His commentary consistently adopts a more critical and analytical perspective compared to his friends' reactions.

Within the series structure, Shigeru fulfills a consistent narrative function across all seasons. He remains an observer and commentator, providing crucial exposition and reaction through his knowledgeable perspective on the magical girls' encounters. His background, personal history beyond school, and significant character development arcs remain unexplored.