Natsukawa

Biodata

Feature	Details
Name	Natsukawa Sosuke (夏川) 2
Gender	Male
Affiliation	Tokyo Metropolitan Advanced Nurturing High School; Class 1-D 2
Occupation/Role	Student; photography club member; information broker and strategist 7 9 13
Status	Active 158
First Appearance	Chapter 2

Power Progression

Stage / Realm / Level	Chapter	Notes
Campus Situational Awareness System	18	Completes and deploys a forum-monitoring tool that filters campus public opinion into intelligence leads; its conclusions are limited by available data and algorithms. 18
Basic Education Knowledge Mastery	18	Purchases the skill to address weaknesses in Japanese and Social Studies, while independently committing to four hours of study daily for 30 days. His subsequent midterm papers demonstrate unusually deep comprehension and original reasoning. 18 32
Stamina enhancement	37	Begins a system requirement of running 4 kilometers daily for a week; after two days, his stamina has already improved slightly. 37
Basic Combat Mastery training	130, 133	The system gives him combat theory and force-application techniques, but his body initially cannot execute them. Fifteen full-effort sparring sessions against Ayanokoji force that knowledge into muscle memory through repeated injury and correction. 130 133
Practical combat proficiency	142	Applies his developed reactions and technique to defeat Ishizaki, Ibuki, Albert, and Ryuen in rapid succession. 142

Background

Natsukawa enters Advanced Nurturing High School carrying a system debt and a practical goal of earning money. He is assigned to Class 1-D, which he considers more suitable for that purpose than Ryuen’s tightly controlled Class C. 2 9

Before enrollment, he taught himself Japanese as an anime fan, passed the N1 examination in college, and later became rusty in spoken Japanese after beginning work. 2

His knowledge of the original story shapes his early choices. After helping Sakura Airi escape a stalker during a photoshoot, he resolves to alter the future in which she is expelled, describing the effort as both saving her and redeeming himself. 7

Appearance

Natsukawa is a tall, slightly thin student with black eyes. He often cultivates an unimpressive or exhausted appearance, particularly when he wants others to underestimate him. 19 26 106

• Tall and slender build. 19
• Black eyes described as difficult to read and quietly pressuring. 26
• Deliberately performs as physically ordinary during school fitness tests. 106

Personality

Natsukawa is outwardly calm, frugal, and frequently lazy in ordinary situations. He prioritizes free necessities, buys a modest laptop rather than an expensive model, and is willing to spend leisure time reading manga, novels, gaming, or napping. 4 34 101

Behind that casual demeanor, he is intensely calculating. He studies people’s insecurities, controls the timing of information, and treats points, secrets, and social relationships as resources. His interventions can be protective—especially toward Sakura—but he is also willing to pressure, deceive, and manipulate people into roles he believes are useful. 9 22 27 93

He is an avid mystery reader and forms one of his most genuine connections with Shiina Hiyori through shared literary discussion. 33 134

Abilities & Skills

Strategic Analysis & Information Warfare

Natsukawa can infer hidden systems and human motives from small behavioral inconsistencies, then turn those findings into leverage.

• Deduced the school’s S-System through analysis of forum-posting patterns and demonstrated the findings to Ichinose and Kanzaki. 13
• Built the Campus Situational Awareness System to monitor opinion trends and identify useful intelligence. 18
• Identified discrepancies in Class C students’ surveillance footage and injury behavior, providing Horikita with the evidence and script that overturned the Sudo case. 55 60
• Recognized the VIP Exam’s assignment pattern, traded VIP information, and arranged cooperation with Class A and Class B while concealing his role. 88 91 99
• Uses psychological pressure to obtain resources, including purchasing past exam papers from an upperclassman. 27

Academic Ability & Tutoring

After initially struggling in Japanese and Social Studies, Natsukawa rapidly develops high-level academic performance.

• His midterm answers show original arguments and solutions rather than mere memorization of past papers. 32
• Tutors Sakura privately, helping her score above 85 in every subject. 19 32
• Organizes targeted review material and assigns study roles for Sakura, Yukimura, Miyake, and Hasebe. 128
• Uses exam scope changes and past-paper access to protect students from Chabashira’s filtering test. 23 26 32

Social Manipulation

Natsukawa reads vulnerabilities quickly and uses selective honesty, implied threats, and favors to direct others.

• Pressures Ichinose into a paid information alliance by presenting the school’s system as an immediate threat to Class B. 9
• Records Kushida’s hidden outburst, then turns their confrontation into a coercive partnership. 22 23
• Uses Kushida to circulate controlled information during the Sudo investigation. 56
• Maintains a misleading “petty merchant” persona around Sakayanagi to lower her guard. 104
• Conceals his involvement in major exam outcomes, allowing other classes to receive credit for plans he shaped. 99

Combat

Natsukawa develops combat ability through system-assisted training and repeated sparring against Ayanokoji.

• Initially possesses technical knowledge without the physical coordination or muscle memory to use it properly. 130
• Improves through repeated full-contact sparring, adapting his movements after each defeat. 133
• Defeats Ishizaki, Ibuki, Albert, and Ryuen with superior timing, reactions, counters, throws, and grappling. 142
• Remains emotionally composed under Ryuen’s intimidation and later breaks Ryuen’s resolve by exposing his hidden ambition to elevate all of Class C. 141 143

Equipment / Items

• Laptop — Purchased for roughly 40,000 points to support his programming work. 4
• Personal terminal and phone — Used for evidence collection, messaging networks, recordings, and negotiations. 22 56 93
• Campus Situational Awareness System — A self-deployed monitoring and trend-analysis tool for the school forum. 18
• Surveillance archive and USB evidence package — Compiles footage, route analysis, and physical inconsistencies for the Sudo case. 55 60

Relationships

• Sakura Airi — Friend, student, and someone he is determined to protect from her original fate. He helps her escape a stalker, tutors her, supports her social anxiety, and responds to threats against her privacy. 7 19 34 37 63
• Ayanokoji Kiyotaka — Classmate, uneasy ally, and sparring partner. Natsukawa uses knowledge of Ayanokoji’s White Room past and father to secure their training arrangement. 2 129 133
• Ichinose Honami — Information client and strategic ally. Their association begins with a one-million-point agreement regarding Class B’s survival and develops into mutual trust. 9 13 91 96
• Horikita Suzune — Initially distrustful classmate who becomes increasingly reliant on his judgment. Natsukawa supplies her evidence, strategy, and scripts in the Sudo case and later guides her response to Ryuen’s sports-festival scheme. 32 60 63 118 119
• Kushida Kikyo — Volatile, coercive ally. Natsukawa knows her hidden nature, repeatedly pressures her into cooperation, and later becomes the person to whom she confesses her insecurities and past motivations. 22 23 98 123
• Karuizawa Kei — A subordinate and operative who seeks security in his power. After intervening in her bullying crisis, Natsukawa imposes rules of loyalty; she later carries out his instructions against Ryuen and during the sports festival. 90 94 95 118
• Shiina Hiyori — Close friend and fellow mystery-fiction enthusiast. Their relationship is built on literary conversation rather than class rivalry or political ambition. 33 134 135
• Ryuen Kakeru — Rival and eventual victim of Natsukawa’s combat and psychological pressure. Natsukawa defeats Ryuen’s group, exposes Ryuen’s private goal for Class C, and warns him against further provocation. 137 142 143
• Katsuragi Kohei — Negotiation counterpart from Class A. Natsukawa leverages Class A’s secrets and VIP information to extract points and cooperation. 78 88
• Hasebe Haruka — Sakura’s protective friend and a persistent skeptic of Natsukawa’s treatment of multiple girls, though she gradually acknowledges his value to Sakura. 128 132 144

Story Role / Major Arcs

Enrollment and Discovery of the S-System

Natsukawa enters Class 1-D, warns Wang Meiyu against overspending the school’s initial private points, and begins investigating the school’s meritocratic structure. He later sells his conclusions about the S-System to Class B. 2 3 9 13

Midterm Exam Countermeasures

After detecting the altered exam scope, he acquires past papers through an upperclassman, distributes them selectively, and supports Sakura’s academic recovery. Chabashira’s review of his exams reveals that his performance far exceeds simple dependence on leaked material. 23 27 32

Sakura’s Stalker Incident and the Sudo Case

Natsukawa becomes Sakura’s main source of support as her stalker escalates from messages to physical photographs. In parallel, he investigates the Sudo incident through surveillance footage and equips Horikita to dismantle Class C’s false testimony. 34 37 55 60

Island and VIP Examinations

During the special exams, Natsukawa exploits information asymmetry between classes. He pressures Class A over its leadership secret, identifies the VIP pattern, sells information before it loses value, and covertly engineers advantages for Class A and B. 78 88 91 99

Sports Festival

After Horikita enters him into several events without consent, Natsukawa plans to use Class D’s defeat to expose its weaknesses. He later directs Karuizawa to disrupt Ryuen’s scheme against Horikita and gives Horikita the means to reclaim Sudo as a useful resource. 108 110 118 119

Conflict with Ryuen

When Class C harms Sakura during a library conflict, Natsukawa openly identifies himself as Ryuen’s hidden opponent. He accepts Ryuen’s challenge, trains with Ayanokoji, then defeats Ryuen and his followers before issuing a final warning. 137 138 129 142 143

Notable Quotes

“Data doesn't lie.” 13

“Now... I'm here.” 137

“A mortal body—how can it fight against genetic instinct?” 143

Trivia

• Natsukawa passed the Japanese Language Proficiency Test N1 through self-study before enrolling. 2
• He prefers mystery fiction and discusses works by Raymond Chandler, Agatha Christie, and Edgar Allan Poe with Hiyori. 134
• Despite his financial focus, he repeatedly spends effort and points on personalized help for Sakura and others. 7 19 155