Shigeru Sanada holds the rank of Major within the 101 Independent Magic-Equipped Battalion. His primary duty focuses on designing and developing Cad Activation Devices (CADs) and specialized equipment for the unit. Prior to the battalion's formation, he served as a first lieutenant in the Defense Army Department's Weapons Development at Okinawa's Onna Air Base. There, he first met Tatsuya Shiba, recognizing his potential and expressing hope for his future—an encounter that significantly influenced Tatsuya's path into magic engineering.

Sanada's expertise centers on magic engineering over direct combat. He engineered the Third Eye, a specialized cartridge-based CAD prototype critical for maximizing the effectiveness of Strategic-Class Magic, specifically Material Burst. He also enhanced the Movable Suit combat suit prototype beyond its original specifications during field testing. While proficient in Barrier Magic with high objective interference strength, its practical use is limited by slow activation speed; he employed it defensively to protect his position during the Okinawa Defense Naval Battle.

Promotions within the classified battalion faced delays after the Yokohama Incident. Sanada's advancement from Captain to Major, deferred from July 2096, was recognized in January 2097. His demeanor presents a calm, approachable, trustworthy, and unassuming exterior, yet internally he is highly intelligent and occasionally cunning, earning him a reputation as one of the battalion's most tactically astute members despite his unthreatening appearance. He maintains a professional dynamic with Harunobu Kazama and a vitriolic yet cooperative rapport with Muraji Yanagi.

The kanji in his name, 繁 (grow thick) and 留 (distillate), reflect aspects of his character. Beyond engineering, Sanada acts as a mentor figure, having directly inspired Tatsuya's career trajectory in magic technology.