Zero

Overview

Zero is the butler of the Tower household and serves Shun Sato. The prologue’s account of Satomi’s flight identifies an old butler at the Tower gates who admits her and her royal knight inside, establishing Zero’s role as the figure who mediates entry into the isolated domain.

Within the family, Mimi calls him Uncle Zero. This small detail places him close to the household rather than simply in formal service. Volume I does not yet reveal his wider history or abilities, but his position at the gate makes him part of every boundary between the Tower and the outside world.

Steward and assassin

Zero is the Tower's impeccably formal butler, an assassin capable of weightless movement, throwing-knife combat, shadow transit and direct telepathy with Shun Sato. He has served Shun for more than twenty years. Beneath his discipline he regards the Sato children as family; Ryuji Sato calls him “Uncle Zero.”

Zero monitors the Tower perimeter through defensive threads and can appear anywhere their warning reaches. When a hooded visitor crosses the boundary, he attempts to kill her after detecting neither mana nor fear. The Three-Eyed Woman freezes him with a blood-red eye, names him her instrument and seed of chaos, implants an unknown command, and removes his memory of the encounter.

After Yumi's death, Zero assumes command with Roku, carries her to the Grand Tree, and blames himself for failing the household. When Ryuji leaves, Shun orders Zero to find but not retrieve him. Zero spends the next stated two years as an invisible guardian, reporting the boy's quests, loneliness, school friendships and recovery. This surveillance is protective but also continues the family's pattern of concealment.

Zero's connection to Shun permits immediate mental alarms over vast distances. He also emerges directly from Shun's shadow and participates with Ryosuke in restraining the cursed Lord before he can attack Ryuji.