Atsugi is the executive commanding officer of Hirame, a secret government organization fighting the "Lost"—mutated humans created by disconnection from the S.H.E.L.L. system. He directly leads the organization's field team in this anti-Lost unit. He also serves as the foster father to Yoshiko Hiiragi, a fellow Hirame member possessing the unique ability to detect the Lost phenomenon, providing her paternal care and guidance since her recruitment. Atsugi is a robust veteran soldier, characterized by his steadfast and dependable nature in duty, with his experience and resilience defining his approach to Hirame's operations against the Lost threat.