Menou, a priestess and executioner, hunts Lost Ones—individuals from a parallel Japan wielding reality-altering Pure Concepts. Her village’s annihilation by a Lost One’s power left her the sole survivor, her soul bleached of memories and emotions. Rescued by Flare, a legendary assassin, Menou trained relentlessly, bargaining her peers’ freedom by vowing to eradicate enough Lost Ones herself. As an executioner, Menou employs deception and disguises to infiltrate her targets’ trust before striking with a concealed dagger. Though her ether reserves are modest, she compensates with precision, leveraging environmental ether and techniques like Guiding Enhancement for agility, Guiding Camouflage for stealth, and advanced manipulation of etheric veins. Her mission to kill Akari Tokitō, a Lost One with Time as her Pure Concept, grows fraught when Akari’s temporal resets defy death. Menou feigns alliance while seeking a permanent solution, only to discover Akari has repeatedly reversed time to save her, erasing her own memories each cycle. Their journey strains Menou’s emotional detachment, sparking reluctant affection and conflict between duty and empathy. Momo, Menou’s devoted aide and childhood friend, complicates matters with unrequited feelings, clashing with Menou’s bond with Akari. Menou’s moral code rejects cruelty, condemning those who exploit Lost Ones, yet she upholds the Necessarily Evil doctrine, believing her executions prevent Pure Concept catastrophes. Uncovering corruption within the Faust, the religious order she serves, Menou confronts Archbishop Orwell’s experiments to exploit Akari’s power and her own origins as a creation of Ivory, a primordial Lost One. Tasked with thwarting the Four Human Errors—cataclysms born of corrupted Pure Concepts—Menou binds her soul to Akari’s to halt her transformation into a Human Error. This grants Menou fleeting control over time but erodes her memories. In a final gambit, she plans to transfer Akari’s consciousness into her body, sacrificing herself to secure Akari’s chance at a normal life. Once a detached weapon, Menou’s journey forces her to navigate loyalty, identity, and sacrifice. Her bleached past, tactical cunning, and fragile emotional ties weave a tale of duty clashing with humanity, where redemption flickers amidst existential threats.