Soushi Shiga commands the Ex-Arm Countermeasure Division as its section chief, leveraging his origins in the National Defense Force and deep military connections. He perceives Ex-Arms as existential threats to humanity, fueling an unwavering animosity that shapes his operational decisions and interactions. This antagonistic stance defines his narrative function within the division's command structure.

Reporting directly to unit head Chikage Rokuoin, Shiga coordinates tactical responses to Ex-Arm incidents while collaborating with engineer Alisa Himegami and exoskeleton soldier Kimura. His physical presence features light grey hair, grey eyes, and consistent military uniform attire reflecting his professional background.