Kokonoe Mercury is a half-beastkin scientist who serves as a leading intellectual figure in Sector Seven. Her background is defined by the legacy of her parents, Konoe Ayatsuki Mercury and Jubei, two of the legendary Six Heroes, though she bears a strong resentment toward her father for abandoning her during her childhood. This experience firmly shapes her detached and cynical personality. She is strict, pragmatic, and often dismissive of emotional considerations, perceiving them as inefficiencies that interfere with her objectives. Her primary motivation is a deep-seated hatred for Yuuki Terumi, the entity responsible for the deaths of her mother and her aunt, Celica. This vendetta drives almost all of her scientific pursuits and tactical decisions. In the story, Kokonoe operates as the strategic mastermind behind many key events, rarely acting directly but manipulating the board from her laboratory. She is the creator of Iron Tager and Lambda-11, and successfully extracted Hakumen from the Boundary. She was the first non-Observer to realize that the world was trapped in a time loop. Her key relationships include Tager, her most trusted agent and primary point of contact; Litchi Faye Ling, a former student; and Jubei, her estranged father, with whom she maintains a cold but functional connection, demonstrated when she agreed to create a new arm for Ragna the Bloodedge at Jubei's request. Her development centers on her grief and her evolving approach to vengeance. While she begins as a solitary figure consumed by her grudge, events force her into broader alliances and compel her to confront the emotional ties she tries to suppress, including the revelation that her mother was still alive but brainwashed. Her notable abilities lie entirely within her scientific genius, which is unprecedented in its scope. Her inventions range from advanced cybernetics to weapons of mass destruction, granting her influence over the world's conflicts from behind the scenes. Her comprehension of the world's true nature and her capacity to manipulate its fundamental laws make her indispensable in the struggle against the forces threatening reality.