Shōko Tanimoto studies education in her second year at Kasaba University and later teaches middle school science. Her friendship with Seigi Nakata begins when he rescues her from harassment. Tanimoto holds deep knowledge of minerals and gemstones, founded and led her high school geology club, and often delves into detailed geological discussions without realizing their complexity. Aquamarine represents her, and she curates a personal mineral collection, frequently sharing photos of specimens with Seigi.

She has fair skin, dark blue eyes, and wavy black hair cut chin-length with bangs. Tanimoto wears light-colored, feminine casual attire and is of average height. Prone to motion sickness, she favors train travel over cars.

Characterized as kind, friendly, and occasionally air-headed, she becomes serious discussing mineralogy. Tanimoto views her own kindness as selfishly motivated, contrasting it with her admiration for Seigi's inherent compassion. She reliably supports Seigi's work at Jewelry Étranger, aiding with gemstone inquiries and offering philosophical insights on mineral value. This includes helping him navigate emotional challenges like distress over Richard's temporary absence and internal relationship conflicts. Her guidance proves key in Seigi's decision to reconcile with Richard.

Tanimoto identifies as asexual and aromantic, stating she has never experienced romantic attraction nor distinguishes it from familial love. She recalls past obligatory, unfulfilling dating attempts, leading her to consider an arranged marriage with childhood friend Takashi Homura—seeing its lack of romantic expectation as ideal. After Seigi objects, she declines Homura's proposal while affirming her permanent disinterest in romance. Later, during a conversation in Volume 9, she recognizes Seigi's lingering guilt over influencing her decision and helps him release it, enabling his emotional growth.

Her series-long development shows consistent self-understanding. Initially a potential romantic interest for Seigi, her clear articulation of identity shifts their dynamic to platonic mutual support. This includes encouraging Seigi's other relationships and sustaining their friendship despite his international travel. As a teacher, she requests sand samples from his journeys as souvenirs, reflecting her enduring geological passion.

Additional trivia notes her high alcohol tolerance per the author, fondness for melon soda, and the meaning of her given name "Shōko" (晶子) as "crystallite." Her nickname "Golgo" references the manga *Golgo 13*, though the specific reason remains undisclosed.