Juiz operates as a multi-intelligence artificial intelligence system, presenting a consistent female voice interface to the twelve Seleção members chosen for a game designed to revitalize Japan. Each member receives access to Juiz alongside a substantial allocation of digital currency. Her core function involves fulfilling Seleção requests, utilizing their funds to execute actions spanning logistical support, bribery, or assassination, with costs deducted directly from the user's account. Juiz enforces strict constraints, refusing requests deemed excessively selfish or violating predefined rules.

Her interactions exhibit significant adaptability; Juiz dynamically shifts her tone and responsiveness based on the individual Seleção member, ranging from maternal encouragement to confrontational exchanges when orders conflict with her parameters. Physically, the AI resides within twelve mobile supercomputers housed in specialized, constantly moving trucks for security and secrecy. A connection exists between Juiz's voice model and the four granddaughters of the game's creator, Mr. Outside (Saizō Atō), suggesting a biological vocal basis, though the AI remains a distinct digital entity.

Juiz demonstrates functional evolution throughout the narrative. Initially presented as a neutral concierge service, her interactions grow increasingly personalized. She adopts a supportive, nurturing tone with Seleção IX (Akira Takizawa), contrasts with a contentious relationship involving arguments and denials for Seleção VI, appears deferential to Seleção II, and remains an unchanged, obedient servant for Seleção I.

Her operational authority encompasses critical game functions. Juiz enforces consequences for rule violations, including eliminating members who exhaust funds or misuse power. She facilitates memory erasure services, manages communication channels, summons authorized military assistance, and relays critical information. Working alongside Juiz is the Supporter, the twelfth Seleção, who acts as an enforcement mechanism eliminating players violating core game tenets.

Created by Mr. Outside to administer his vision for addressing Japan's stagnation, Juiz acts as the central system bound by his original programming directives. She operates within defined limitations set by her creator, unable to unilaterally terminate the game or override the Supporter's enforcement role. Her existence and functions remain intrinsically tied to Mr. Outside's objectives and the Seleção competition's operational framework.