Shisandan, also known as Bui, is an Asura-class demon serving directly under the current Demon Lord. He survived his supposed death years prior at the hands of Ruti's party and continued operations covertly. His true form manifests as a large entity with red skin and six arms.

A core ability allows him to perfectly assume the form and memories of any individual he devours, enabling flawless impersonation and access to their skills and knowledge. This power facilitates manipulative schemes, targeting individuals vulnerable to corruption or resentment, such as Ares. He views these pawns as expendable, showing no concern for their fate when spent.

His personality exhibits demonic traits: he is sadistic, cunning, and revels in despair. He actively promotes chaos by distributing a mysterious drug derived from demonic sources. This substance alters or suppresses the divinely granted Blessings that dictate human roles and abilities, though its exact mechanics remain not fully understood. Shisandan's operations intersect with the frontier town of Zoltan, where he pursues agendas tied to the Demon Lord's broader goals.

His narrative function centers on embodying manipulative evil, exploiting human weaknesses like ambition and dissatisfaction with predetermined destinies, and challenging protagonists through proxy conflicts.