Munin, a member of the Game Police, partners with Hugin to enforce operational integrity within the Deca-dence entertainment facility. Their duty involves identifying and eliminating disruptive "bugs." Communication occurs primarily through mechanical "peep-peep" sounds, though Munin and Hugin understand each other. Despite a cute, colorful appearance featuring multiple expressive faces on a spherical mechanical body—with the primary face being purple—Munin exhibits severe judgment toward system non-conformity.

Named after one of Odin's ravens, Munin's design consistently reflects this avian motif. The character appears alongside Hugin, forming a duo that functions almost as a single entity with shared purpose. Initially presented as Hugin's subordinate or companion, a significant revelation exposes Munin as the true administrator of Deca-dence, the hidden authority directing system operations rather than merely assisting Hugin. This shift establishes Munin as the primary orchestrator maintaining the facility's rigid order.

Actions consistently enforce system protocols. Munin participates directly in ambushes targeting perceived threats, such as the confrontation at the Gadoll factory where Kaburagi and Natsume are cornered. The character employs the recurring declaration "There is no place for bugs in this world," underscoring an unwavering commitment to eliminating anomalies and preserving Deca-dence's controlled environment as a primary antagonist.