Sadako Shimohara hails from Onomichi, Hiroshima, in Fuso, born into a scholarly family immersed in literature and history. She abandoned scholarly ambitions when her magic powers manifested, leading her to join the Naval Flight Academy. Her academic foundation contributed to strong classroom performance, resulting in graduation as a Sergeant before European deployment.

Assigned to Libau base, she endured rigorous combat training under Mio Sakamoto. Initially overwhelmed, she often retreated to the sidelines during drills, seeking comfort from peers like Takei. This demanding training later proved vital for survival on the harsh Eastern Front, particularly in Karlsland. There, she participated in nighttime combat operations alongside Karlslandian night witches, conducting joint missions with ground command posts and defending against night raids despite lacking magic needles for wide-area searches.

Transferred to the 502nd Joint Fighter Wing in Petersburg, Orussia, she adopted a maternal role. Her nurturing personality and exceptional culinary skills, especially in Fusoan dishes like nikujaga and miso soup, earned her appreciation from squadron members, notably Naoe Kanno. This bond fostered unit-wide jokes about their "parent-child" dynamic. She actively promoted Fusoan culture, introducing practices like seiza (formal sitting), though the unit repurposed it as disciplinary punishment rather than her intended mental training. Her personal belongings included Fusoan novels and traditional clothing.

Her personality blends warmth with a notable fondness for "small and cute" individuals, leading to frequent hugging that some portrayals humorously label as "creepy old man" behavior. Her closest bond is with Georgette Lemare, whom she calls "Sada-chan"; they share girlish interests appropriate for their age. She also formed casual friendships through cultural exchanges, such as cooking for the notoriously hard-to-please Kanno.

In combat, she possesses composite magic vision granting long-range sight and night vision. This makes her adept at reconnaissance, patrols, and danger sensing, though she struggles to teach these skills. Her equipment includes a Striker Unit modeled after the Kawanishi N1K Shiden and a Type 99 machine gun. While proficient in wilderness survival and target acquisition, she harbors self-doubt about her abilities.

Her familiar is the Japanese hare, and her magic activation manifests as hare-like ears and a tail. She is based on the historical Japanese flying ace Uehara Sadao.

In *World Witches: Take Off!*, she appears as part of the 502nd's daily life in St. Petersburg, engaging in activities like winter swimming with Nikka Katajainen and Hikari Karibuchi. Her cooking remains central to unit morale, with noticeable disappointment arising when meals are not prepared by her. The series alternates between the 502nd's training of Hikari and the 501st's activities, though no direct crossover occurs between the units.

Expanded media, such as Twitter stories, detail her integration into the 502nd. Upon arrival, she observed unit dynamics during Commander Rall's introduction, witnessing Waltrud Krupinski's reckless landing and Edytha Rossmann's subsequent frustration. Her magic eyesight aided in identifying returning squadron members like Nikka, Naoe, and Georgette during this initial assessment.

In fan-fiction expansions like the XP4 Heroes Coalition series, she participates in combat against Emotionless-Neuroi hybrids and alliance-building events alongside the 502nd, maintaining her supportive role during missions and base interactions.