Kōga Tatsuma operates as a police officer in Akatsuki Special Zone's Public Safety Bureau, one of three entities upholding order in the lawless territory. At 36 years old, he bears a Divine Tattoo marking him as a Scard—granting near-invulnerability against blades and bullets through sealed divine powers. His duties involve monitoring fellow Scards while deploying his own abilities for law enforcement.

Available records reveal little about his origins, though he demonstrates pragmatic, goal-driven methods. Outwardly good-natured, this demeanor conceals a readiness for extreme measures to accomplish objectives. He maintains a professional rapport with colleague Itsuki Torataka, a 17-year-old Scard officer whose combat skills differ from Kōga’s experience. Kōga routinely advises Itsuki, though such guidance faces frequent dismissal.

Physically, he stands 188 cm tall with dark green hair trimmed to neck length and brown eyes, projecting a composed presence. Childhood and family connections remain undocumented.

During organizational conflicts, he sides with the Public Safety Bureau alongside Itsuki, distinct from factions like Helios or Artemis. His actions strategically prioritize institutional stability amid the zone’s volatility. Across media, his portrayal remains consistent without deviation in core motivations or role.