Siesta, codenamed the legendary detective, operates under a veil of secrecy, her true identity—name, age, and nationality—shrouded in mystery. As the Twelve Tuners’ esteemed Great Detective, she combats global crises with a musket and seven uniquely empowered tools.

Her arresting presence blends a monochrome goth lolita ensemble—grey jacket, black blouse, ruffled skirt, tights, and Mary Janes—with stark white hair styled in a chin-length bob. Sky-blue eyes pierce beneath a hairpin marked "XII," accentuating her poised, enigmatic aura.

A genius strategist, she unravels cases before they crystallize, her intellect rivaled only by superhuman agility: bullet-dodging reflexes and evasion of high-speed assaults fuel theories of artificial creation. This fusion of mind and might informs her preemptive strikes against threats.

Four years pre-narrative, she recruits Kimihiko Kimizuka during a hijacking, forging a three-year partnership to dismantle SPES-linked cases. Her protectiveness toward him surfaces in crises, occasionally tinged with possessiveness when others encroach.

In a calculated gambit, she sacrifices herself to eliminate Hel, SPES’s linchpin antagonist. Her transplanted heart imbues Nagisa Natsunagi with cellular memories, sparking shared dreams, inherited traits, and spectral guidance—a haunting legacy implying unresolved consciousness.

Former Twelve Tuners operative and SPES saboteur, her origins remain obscured, though her meticulously planned demise underscores a lifetime of strategic warfare. Expanded lore explores her pivotal role in the conflict, her posthumous impact echoing through Nagisa’s psyche and flashbacks. Initially a peripheral figure, her narrative prominence surged with the series’ success, cementing her as the architect of enduring victories and emotional anchors within the story’s core.