Tatsuya

Biodata

Background

Tatsuya belongs to the Shiba branch of the Yotsuba Family. Members of the family nearly killed him immediately after his birth, a secret he does not know. Maya and Hayama recognize that he feels no loyalty to the Yotsuba, but Maya nevertheless entrusts him with Miyuki’s safety 3.

An earlier attack on Miyuki by Okinawan rebel soldiers left Tatsuya particularly intolerant of betrayal. This history shapes his reaction when he discovers that Zhou Gongjin is being sheltered inside a National Defense Force base 6.

Appearance

• Build: Sturdily built and visibly strong; a hotel bartender mistakes him for a bodyguard 4 5.
• Eyes: Naturally sharp, making a deliberately angry expression especially intimidating 4.
• Expression: Frequently expressionless, including when sincerely reassuring Minoru 5.
• Operational clothing: Uses a motorcycle helmet to conceal his face during covert activity and wears blade- and bullet-resistant clothing for the Uji operation 5 6.

Personality

Tatsuya is pragmatic, guarded, and willing to use deception or intimidation to obtain results. He pressures a private detective through activated psions and a bluff involving his watch, demands evidence rather than accepting a Traditionalist leader’s assurances, and infiltrates a military base despite knowing the legal consequences 4 6.

His emotional intensity has an upper limit. When anger reaches that threshold, his voice loses emotion and conveys only intent. Discovering the military’s involvement in sheltering Zhou triggers this response 6.

His reserve does not prevent consideration for others. He reassures Minoru that illness has not diminished his value as a companion, tries to keep Mayumi out of the Zhou operation, and credits Miyuki and Masaki for their contributions in battle. Miyuki’s distress can also overcome his resolve: her pleas persuade him to share the disturbing truth he discovers about Minoru’s birth 5.

Abilities & Skills

Elemental Sight

Tatsuya reads structural information, causes, and origins through Elemental Sight, extending his perception beyond outward appearances 5.

• Information analysis: Reads how something was made and the circumstances behind its present condition 5.
• Tracking: Memorizes the information in Nagura’s blood, then locates that blood inside Zhou despite Demon Gate Dunjia obscuring Zhou’s position 5 6.
• Magical detection: Perceives psion threads, concealed opponents, and disturbances that reveal a hidden controller’s location 5.
• Reading past movements: Obtains the coordinates of a Traditionalist hideout from an unconscious attacker. The target’s intact Eidos and suppressed psion emissions make the reading easier 5.
• Limits: A photograph of Zhou is insufficient as a search key. Scanning Kyoto without a stronger clue would take an indeterminate amount of time 4.

Decomposition

Tatsuya can dismantle physical objects and magical structures, selecting specific components rather than destroying an entire target 5 6.

• Decomposes the suppressive noise transmitted through enchanted silk cords while leaving the cords intact 5.
• Severs the psion threads controlling weaponized dharma wheels 5.
• Cuts bamboo above concealed attackers as a warning, forcing them out of hiding 5.
• Dismantles surveillance cameras, firearms, and vehicle components during the Uji infiltration 6.
• Secretly uses an area-setting Decomposition spell against live rounds that penetrate Masaki’s defense 6.
• Can accurately use Decomposition without a CAD at the close range encountered in the Arashiyama ambush 5.

Flash Cast and Close-Quarters Combat

Flash Cast lets Tatsuya integrate rapidly activated magic into physical attacks 5.

• Vibration strike: Activates vibration magic immediately in front of his palm, transmitting vibrations through an opponent’s bodily fluids and incapacitating him 5.
• Aerial movement: Creates magical footholds and repulsion fields to redirect himself in midair and accelerate flying kicks 5.
• Anticipation: Moves before an enemy’s electric-shock spell activates rather than attempting to dodge the lightning after release 5.
• Physical limits: He is strong but does not possess inhuman strength; pulling two attackers from cover succeeds because his counter-magic first leaves them stunned 5.

Magic Engineering and Analysis

Tatsuya develops and adjusts activation sequences, evaluates unfamiliar spells, and adapts equipment to a user’s needs 4 5.

• Optimizes the activation sequence used with Leo’s thought-operated CAD 4.
• Adds a power limiter to Miyuki’s cooling spell so that it induces hibernation rather than killing its targets 5.
• Arranges for FLT’s third development division to produce Erika’s weapon-integrated CAD for the Kyoto reconnaissance 4.
• Deduces that the Uji River barrier uses a magical medium flowing downstream rather than a continuously maintained spell covering the entire river 4.
• Identifies a Phantasmal Beast as the likely cause of Nagura’s fatal wound and explains how its strength depends on the victim’s perception 5.

Psion Body Examination

At Fujibayashi’s request, Tatsuya examines Minoru’s Psion Body and proposes an explanation for his recurring illness 5.

• Identifies exceptionally active psions damaging the conduits of Minoru’s Psion Body, with the damage feeding back into his physical body 5.
• Explains that rapid damage and repair occur in short cycles 5.
• Suggests suppressing psion activity or strengthening the Psion Body, but does not know how to accomplish the latter 5.
• Also discovers Minoru’s origin during the examination; the revelation overwhelms him and later concerns Miyuki 5.

Baryon Lance — In Development

Tatsuya is developing a new spell called Baryon Lance, with an unveiling planned for the New Year Celebration 3.

• Its development references Angie Sirius’s Brionac 3.
• Hayama conjectures that it breaks matter down into protons and neutrons and likely functions as a neutron cannon 3.
• Its actual mechanism is not demonstrated in the supplied events; Maya and Hayama’s discussion remains speculative 3.

Equipment / Weapons / Items

• Silver Torus: Prototype bracelet-shaped specialized CADs worn on both wrists. Linked aiming-assistance antennas compensate for their shorter length compared with gun-shaped CADs 5.
• Fully thought-controlled CAD: Worn below his chest and used with the Silver Torus as an experimental hands-free casting setup. Tatsuya finds the combination slightly awkward despite using it effectively 5.
• Silver Horn: His alternative CAD, which he does not bring to the Arashiyama investigation 5.
• Multifunction watch: Linked to his information terminal. It has no magic-assistance function, although he successfully bluffs a nonmagician into believing otherwise 4.
• Motorcycle: Owns one; the Kuroba twins provide the same model for the Uji operation 4 6.
• Combat clothing: Blade- and bullet-resistant clothing, plus combat boots, gloves, and a belt supplied by Fumiya and Ayako 6.
• Helmet communications: Uses a helmet-linked wireless connection to operate his information terminal by voice while riding 6.

Relationships

• Shiba Miyuki — Younger sister and the person whose safety he is entrusted to protect. Her concern weighs heavily on his decisions, and he assures her that his “eyes” remain on her even while they are apart 3 5.
• Yotsuba Maya — Assigns him the pursuit of Zhou as a request rather than an order. She treats the assignment as a test and later defends his usefulness before the branch-family heads 2 7.
• Hayama — Receives mission information and reports through the Yotsuba network. He argues that Tatsuya’s actions and results matter more than personal loyalty 3 5 6.
• Kudou Minoru — Guide and investigative companion. Tatsuya values his help, examines his illness, and learns the secret of his birth 2 5.
• Fujibayashi Kyouko — Military contact and intermediary with the Kudou Family. She requests Minoru’s examination and later warns Tatsuya against entering the Uji base 5 6.
• Saegusa Mayumi — Senior school acquaintance who asks him to investigate Nagura’s murder. He helps her while attempting to keep her away from the operation against Zhou 3 5.
• Ichijou Masaki — Combat ally whom Tatsuya considers troublesome as an enemy but reliable as a partner. Tatsuya reveals his military position to him and recruits him for the Uji infiltration 4 6.
• Kuroba Fumiya and Kuroba Ayako — Deliver Maya’s request, provide intelligence and equipment, and coordinate the effort to prevent Zhou’s escape 2 6.
• Yoshida Mikihiko, Chiba Erika, and Saijou Leonhart — Friends who conduct a parallel investigation around the Thesis Competition venue and share their findings with him 4 5.
• Zhou Gongjin — Mission target and Nagura’s killer. Tatsuya defeats his concealment by tracking Nagura’s blood embedded in his body 2 6.

Story Role / Major Arcs

Pursuit Through Nara and Kyoto

In late September 2096, the Kuroba twins bring Tatsuya Maya’s request to help capture Zhou Gongjin, who has fled Yokohama. Tatsuya visits the Kudou Family in Nara, meets Minoru, and follows him to a Traditionalist stronghold sheltering Zhou 2.

He later returns to Kyoto with Miyuki and Minami under official leave nominally granted for Thesis Competition preparations. While Mikihiko, Erika, and Leo investigate near the competition venue, Tatsuya’s group searches likely Traditionalist bases. He exposes a detective watching Minoru and obtains information from the detective’s employer, a Traditionalist faction leader who claims to have abandoned the conflict 4.

Nagura’s Murder Investigation

Mayumi asks Tatsuya to help investigate her bodyguard’s death. At the police evidence room, he examines Nagura’s belongings, infers a Phantasmal Beast attack, and secretly records the information in Nagura’s blood. He concludes that Nagura likely used his own blood for a final counterattack 3 5.

At Arashiyama, ancient magicians ambush Tatsuya, Miyuki, Mayumi, and Masaki. The group subdues them, and Tatsuya later follows information read from one attacker to their hideout. He defeats the remaining practitioners and passes the location and intelligence to Fujibayashi 5.

Minoru’s Illness and Birth Secret

After Minoru develops a fever, Fujibayashi asks Tatsuya to investigate his Psion Body. Tatsuya identifies a cycle of psion-induced damage and repair, but also discovers that Minoru is an Adjusted Body and Fujibayashi’s maternal half-brother 5.

He later tells Miyuki that Minoru is the biological child of a brother and sister, probably conceived through artificial insemination. He cannot establish whether Minoru’s illness results from that parentage or from something going wrong during adjustment 5.

Uji Second Supply Base Operation

The Kuroba Family traces Zhou to the National Defense Army Uji Second Supply Base. Fujibayashi confirms the location but asks Tatsuya to leave the matter to the military police. He instead recruits Masaki and infiltrates the base while the Kuroba group prepares to intercept Zhou outside 6.

Tatsuya and Masaki disable weapons and vehicles as Zhou escapes through the south gate. After Minoru, Ayako, and Masaki hinder the escape, Tatsuya corners Zhou by the Uji River. Tracking Nagura’s blood allows him to counter Zhou even when Demon Gate Dunjia prevents him from knowing Zhou’s own position 6.

Masaki disables Zhou’s legs with Rupture. Zhou then bursts into flames and vanishes, leaving Tatsuya convinced that he has not escaped. Tatsuya thanks the Kuroba twins and asks Fumiya to report the assignment’s completion to Hayama 6.

Thesis Competition and Yotsuba Assessment

At the 2096 Thesis Competition, Tatsuya tells Mayumi that Nagura’s killer took his own life. He praises First High’s Engraving-Type Magic presentation, but Second High wins after Minoru presents its hypothesis concerning Mental Interference Magic 7.

Meanwhile, Maya presents Tatsuya’s successful assignment to the Yotsuba family heads as evidence that he can fulfill his responsibilities without compulsion. Their opinions remain divided, and a final judgment is postponed until the New Year Celebration 7.

Notable Quotes

“No matter how old you are, you're still my little sister.” 5

“I don't know where you are. But I know the whereabouts of Nagura Saburou's blood on you.” 6