Chiba Yeyou

Biodata

Power Progression

Yeyou’s documented development centers on spell research and CAD engineering rather than advancement through personal cultivation realms.

Background / History

Childhood and Research

According to Yakumo Kokonoe’s investigation, Yeyou grew up in a suburban villa and lost his parents in a car accident at seven. He subsequently lived alone, supported by inherited assets, and displayed exceptional magical talent. Yakumo could not obtain detailed information about the period beginning five years before their investigation; during that time, Yeyou remodeled his home and purchased surrounding properties at a cost exceeding his inheritance 48.

Yeyou is a transmigrator who recognizes people and circumstances from his prior knowledge of the setting. Early in his school life, he consciously reminds himself that Mayumi Saegusa is a living person rather than an anime character. His later interventions also change the course of events he remembers 2 20 135.

Tiffany supplies resources for his research, and money earned through her enabled him to acquire his extensive home and grounds. Before she moves in, he is accustomed to an otherwise silent household 15 35.

Enrollment at First High School

Yeyou chooses First High partly to study the magic of its elite students, particularly those connected to the Ten Master Clans. Apart from Quantum Domain and its associated innate magic, his own spells are products of research and development informed by studying other techniques 109.

His first encounter with Mayumi involves falling from a rooftop while distracted by her. Although he is ready to use magic, he allows her to catch him instead. Their subsequent teasing quickly generates schoolwide rumors of a romance 1 5 6.

He befriends Tatsuya Shiba despite the division between Course 1 “Blooms” and Course 2 “Weeds.” He later helps with Student Council paperwork and patrols the campus with Erika Chiba during club recruitment 2 30 40.

Blanche Incident

During the armed attack on First High, Yeyou helps Mari Watanabe clear the campus’s eastern area. He uses lethal magic against armed intruders but keeps one magician alive to lead him to Blanche’s hideouts 50.

Carrying his captive through the air through gravity manipulation, he destroys multiple locations; by one point, he has already visited seven. The resulting devastation reveals the scale of his offensive magic to his schoolmates. Afterward, Katsuto Jumonji privately urges Mayumi to pursue him, believing he should be brought into the Ten Master Clans 53 54.

Nine Schools Competition

Yeyou joins the technical support team after demonstrating his CAD-adjustment skills on Mayumi’s device. His principal assignments are Mayumi and Mari, whose performances improve through his tuning and specialized magic. He also competes, with Icicle Destruction among his scheduled events 58 69 75 81 83.

He helps identify the Battle Board sabotage as spirit magic and connects attempts to interfere with First High’s results to No Head Dragon. After killing two men who try to recruit him as an inside agent, he warns that the organization might escalate to stopping the competition altogether 94 104.

Yeyou later participates in Monolith Code, where restrictions on highly lethal magic limit his usual options. He and Tatsuya subsequently eliminate the leadership of No Head Dragon’s Japanese branch, earning thanks from Harunobu Kazama and his personnel 124 137.

Detention Center and Yokohama

At the detention center, Yeyou confronts Lü Ganghu alongside Mayumi and Mari. Lü uses a defensive sequence prepared specifically against Yeyou’s magic to block his white beam, but Mari exploits the opening and incapacitates him 151.

During the Yokohama International Conference Center attack, Yeyou directs students against intruders and uses Cloud Mist and Ashes while clearing the building. On learning that another group is evacuating through an underground passage, he sends Hattori and Zemu after them to prevent a collision with enemy forces 157.

Personality

Yeyou presents himself as lazy, irreverent, and fond of provoking others. He routinely sleeps through lessons, exchanges flirtatious barbs with Mayumi, and treats school confrontations as entertainment. His apparent inattentiveness can conceal intensive work: an afternoon spent looking like an attentive student is actually devoted to billions of CAD-design simulations 6 11 12.

His approach to magic emphasizes curiosity, precision, and innovation over prestige or brute force. He challenges the assumption that Course 2 placement makes someone inferior and argues that a magician’s willingness to develop and test new ideas is more valuable than strength alone. Although he sees magic’s civilian potential, he does not consider civilian development and military strength incompatible 3 21 32 34 97.

Beneath his confidence, he carefully weighs political exposure and the risks of sharing his research. He dislikes the prospect of marrying into a powerful family merely for protection, but willingly builds friendships that could provide support. His growing understanding of Quantum Domain also tempers his early arrogance about his own inventions 16 43 72 116.

He can be considerate toward friends while remaining ruthless toward enemies. He comforts Miyuki over her worries about Tatsuya, cares for Tiffany after she falls asleep beside his work, and uses lethal force against armed attackers without hesitation 27 47 61.

Abilities & Skills

Quantum Domain

Yeyou’s innate ability underlies much of his magic, including techniques that other magicians cannot reproduce simply by learning their principles 54 90.

• Supports spell analysis, information gathering, simulations, and the development of new magic 11 19 109.
• Provides the foundation for Constant Force Deflection and many of his other specialized techniques 54.
• Allows him to mobilize practically unlimited psions despite having finite personal reserves; his effective constraints are output and application 87.
• Remains only partially understood by Yeyou himself. He compares his position to possessing a vast treasury without its key 109.

Situational Awareness and Microscopic Insight

Yeyou uses Situational Awareness to obtain information about spells and locate threats. He later names his real-time surveillance capability Microscopic Insight, describing it as a byproduct of Quantum Domain 19 50 123.

• Analyzes magic, spirits, and physical phenomena, including dynamic and solid-state information 64.
• Can obtain information about living and nonliving matter 65.
• Usually functions as an early-warning system; Yeyou says he does not ordinarily inspect other people’s information 65.
• Operates within Quantum Domain. No numerical range is established 123.
• Makes otherwise invisible attacks perceptible to him, including Shinkuro Kichijoji’s air bullets 124.

Constant Force Deflection and Gravity Manipulation

An innate application associated with Quantum Domain, Constant Force Deflection supports both movement and control of targets 47 54.

• Pulls fleeing attackers back toward him 47.
• Enables gravity-based aerial movement, including carrying another person 53 54.
• Is distinct from the generally usable flight magic Tatsuya is developing 53.
• Cannot readily be distributed as ordinary magic; reproducing it for others would require substantial work on antigravity 54 60.

His protective system also activates Gravity Imbalance to slow his fall after Miyuki knocks him through a classroom window 6.

Defense Countermeasure

A self-developed defensive spell that initially combines protection with automatic retaliation. Although Yeyou originally calls it innate magic, he later acknowledges that this description exaggerated his achievement 6 116.

• Automatically protects him from Miyuki’s punch and begins a retaliatory strike, which he manually cancels 6.
• Returns gunfire along its original trajectories and reflects hostile spells 47 103.
• Initially provides useful protection against anti-magician bullets but proves insufficient against certain magic 116.
• Is redesigned as dedicated defense rather than a defense-and-counterattack hybrid 116.

Ashes and Offensive Magic

Ashes is Yeyou’s self-developed A-rank attack, released as a ghastly white beam through his CAD 47 109.

• Incinerates people and firearms within seconds 47.
• At unrestricted combat output, pierces trees and causes a large boulder to liquefy and disappear 132.
• Is difficult to adapt to competition rules limiting highly lethal magic; a reduced-power version fails to overcome Kichijoji 124.
• Is not universally unblockable: Lü Ganghu counters Yeyou’s white beam with a specially prepared shield 151.

Other named techniques include Flame Hell, Quantum Streamline, and Quantum Vacuum. Tatsuya supplies the name Quantum Streamline; Yeyou states that Quantum Vacuum has major restrictions, without detailing them in the available account 109 137 141.

Precision and Simultaneous Casting

Yeyou advocates achieving a desired effect with the smallest necessary expenditure of psions. His demonstrations distinguish precise interference and compression from merely increasing destructive power 21.

• Compresses a light spell while increasing its brilliance 21.
• Demonstrates small-scale versions of Niflheim while teaching Miyuki 43.
• Can activate two different spells through a single CAD without the usual interference between their Activation Sequences 72.
• Treats simultaneous casting as closely guarded research rather than a routine technique 72.
• Requires his own construction system and personal approval for access to his core magic 43.

CAD Engineering and Spell Development

Yeyou researches commercially available CADs, studies their internal systems, and constructs customized devices. Mayumi finds his manually adjusted CAD unusually smooth to operate 27 58.

• Tunes Mayumi’s CAD to improve activation speed and tracking 83.
• Installs a defensive program in Mari’s CAD 94.
• Develops Light Energy Pulse for Mari’s Battle Board use: each activation lasts half a second, cannot be repeated continuously, and consumes enough psions that roughly five uses would exhaust her ability to cast 75.
• Produces competition enhancements that are exclusive to him and will not remain available after the event 98.

Information Technology

Yeyou possesses advanced intrusion and defensive capabilities. Tatsuya reports that his own first hacking teacher—the “Electron Sorceress”—lost to Yeyou in information intrusion 79.

Limitations

• Martial arts: A recognized weakness. Yeyou does not believe he can quickly acquire Tatsuya’s level of close-combat training, even with Tiffany’s assistance 116.
• Restricted competition combat: Many of his preferred spells are too lethal for tournament use, reducing his available responses 124.
• Dependence on Quantum Domain: His own performance is not a reliable benchmark for ordinary users, and others cannot necessarily reproduce his techniques faithfully 76 90.
• Incomplete theoretical understanding: Constant Force Deflection and Quantum Domain exceed what he can fully explain or reproduce through ordinary magical research 54 109.

Equipment / Weapons / Items

• Handgun-shaped CAD — Used to activate Ashes and other combat magic 47 132.
• Competition-issued pistol CAD — Used during the Nine Schools Competition; sufficient for his needs despite not being his personal device 87.
• Ring-shaped CAD — A device he builds for Tiffany, who wears it on her right ring finger 27.
• Purchased research CADs — Includes Yotsuba Clan Technology products, which he rates as the best-performing systems he has studied 11 27.
• Home laboratory — A large basement experimental area beneath his two-story Chinese-style home. He also accesses a concealed room using Quantum Domain 7 35.

Relationships

• Mayumi Saegusa — Senior, technical-support partner, and developing romantic interest. Yeyou describes them as “more than friends but not quite lovers.” She offers her family’s protection and arranges for someone to watch over him 58 98 123 137.
• Tiffany — Longtime friend, research patron, and housemate whom he introduces as his older sister. She supplies materials and funding, while privately viewing him as a prospective husband she has known since childhood 15 26 27 35 75.
• Tatsuya Shiba — Friend, fellow engineer, and combat collaborator. Tatsuya becomes wary of Yeyou’s information-gathering ability but remains grateful for his help to Miyuki 58 65 114 137.
• Miyuki Shiba — Classmate and magic pupil. Yeyou teaches her compression, control, and advanced casting while keeping the siblings’ identities secret; he also promises to help if she needs him 21 43 72 110 111.
• Erika Chiba — Friend and patrol partner with whom he frequently bickers. He supports her Public Morals Committee appointment and recognizes her combat ability 21 22 30.
• Mari Watanabe — Senior and beneficiary of his CAD tuning and experimental magic. They cooperate during campus attacks and the confrontation with Lü Ganghu 50 75 94 151.
• Katsuto Jumonji — Senior who recognizes Yeyou’s strategic value, supports testing his engineering skills, and warns him to control his magical output 54 58 119.
• Kyoko Fujibayashi — Military contact with whom he exchanges intelligence and teasing remarks. She later approaches him for help investigating covert surveillance around First High 133 143 144.
• Harunobu Kazama — Military officer interested in his abilities and unknown backing. Kazama seeks friendly relations and eventually places Yeyou’s importance no lower than Tatsuya’s 79 104 154.
• Suzune Ichihara — Senior who recruits his help with Student Council paperwork and teases him about Mayumi 7 40 98.

Notable Quotes

“A true master always keeps an apprentice's heart!” 3

“I pay more attention to how magic performs, achieving what I want at the smallest possible cost.” 21

“What magic is used for depends on the person using it.” 32

“I don't like starting trouble, but I'm not afraid of it either!” 130