Mu Tianchen

Biodata

Feature	Value
Name	Mu Tianchen (沐天辰)
Alias(es)	“Mysterious Boy” 31
Species/Race	Human
Gender	Male 3
Affiliation	Kodo Ikusei High School; First Year Class D 3
Occupation/Role	Student; points strategist and temporary Class D collaborator 27
First Appearance	Chapter 2: “Enrollment” 2

Background / History

Mu Tianchen grew up under the direction of his father, Mu Tianxiao. His parents chose his enrollment at Kodo Ikusei High School without seeking his opinion; his father had already made him study the local language and introductory material, while his mother opposed sending him away for three years. Tianchen regarded the move with resignation rather than enthusiasm. 2

As a child, Tianchen was taken by his father to a remote, white facility where he witnessed children being trained under harsh supervision. There he saw Ayanokouji Kiyotaka, identified by Mu Tianxiao as the facility’s greatest creation and the intellectual and combat standout of the Fourth Generation. Mu Tianxiao urged Tianchen to regard Kiyotaka as his goal. 4

Before entering Kodo Ikusei, Tianchen had been highly successful and surrounded by admirers. He later realized that he had ignored sincere warnings, lost the friends who tried to correct him, and suffered a collapse after mistaking popularity for genuine leadership. This experience left him reluctant to lead others and inclined to act alone. 10 27

Appearance

Mu Tianchen is described as a slender, good-looking young man whose physique reflects long-term physical training. Despite his outwardly unassuming appearance, he possesses exceptional strength. 3 5

• Trained, well-developed musculature. 3
• Often presents himself as timid, quiet, and inconspicuous to avoid attention. 4 15
• Has enough physical presence and attractiveness to draw notice from classmates and teachers. 4 23

Personality

Tianchen is observant, calculating, and strongly independent. He quickly treats Kodo Ikusei as an artificial version of society, where strength, information, and points determine one’s ability to control events. He favors exploiting loopholes and acting from secure positions rather than relying on goodwill. 2 7 11

Although he deliberately performs shyness and mediocrity in public, he is neither passive nor naïve. He conceals his capabilities, studies people’s motives, and uses leverage when necessary—whether bargaining with Ryuen, gambling against club members, or coercing Kushida with recorded evidence. 4 6 15 36

His isolation is tempered by a desire to change. Tianchen values his genuine connection with Hiyori Shiina, regrets how he treated former friends, and recognizes that leadership without true strength and trust is hollow. 10 12

Abilities & Skills

Observation and Deduction

Tianchen routinely identifies hidden structures and motives from small details.

• Deduced that Class D’s behavior would trigger a point-based penalty system and located a concealed classroom camera. 7
• Recognized that the school deliberately leaves certain areas unwatched, allowing students to exploit gaps in surveillance. 11
• Identified the unusual test as a likely attempt to locate exceptional students rather than a harmless assessment. 18
• Assessed Ryuen’s response to blackmail to determine that he possessed broad strategic judgment and influence over Class C. 6

Strategy and Point Manipulation

Tianchen treats personal points as both currency and political power.

• Obtained evidence of Ryuen’s scheme involving upperclassmen, then secured 360,000 points in exchange for deleting it. 5 6
• Used controlled table-tennis betting to exploit opponents’ overconfidence while concealing his actual skill. 15 17
• Amassed more than 1.5 million points through his existing funds and winnings from the Table Tennis Club. 17 19
• Negotiated with Chabashira Sae to assist Class D’s midterm effort in exchange for an exceptional reward based on class-point gains. 27
• Understands that a Class Transfer Right costs 20 million points and considers accumulating enough points to obtain one. 32 38

Martial Arts and Physical Strength

Tianchen trained in martial arts from childhood under his father and instructors brought from the Island Nation. He has achieved success in prior competitions. 5

• Easily evaded, disarmed, and defeated three upperclassmen in an unwatched area. 5
• Is physically strong enough that Kushida could not move his arm when attempting to manufacture evidence against him. 35
• Maintains a regular running routine at the school track. 11 19

Table Tennis

Tianchen is an exceptionally skilled table-tennis player who weaponizes pacing and deception.

• Deliberately plays at a lower level to make opponents believe they have a chance before taking decisive points. 15
• Defeated multiple senior members of the Table Tennis Club in succession. 16
• Beat vice-captain Miyamoto Subaru 3–0 after intentionally withholding his full ability early in the match. 17

Chess

Tianchen has substantial chess experience and believes his ability is at least professional level after repeatedly practicing against Arisu. 14

• Planned to use the Chess Club as a second source of betting income, though the Table Tennis Club alone nearly fulfilled his immediate financial target. 14 17
• Remains confident in a future match with Sakura Arisu. 43

Equipment / Items

• Student phone / S System account — Holds his student identification and personal-point balance. 3
• Voice recorder — Purchased after studying the school’s surveillance gaps; used to record Kushida’s hostile behavior and secure leverage over her. 11 35
• Past examination papers — Purchased from Takagahara for 250,000 points to support Class D’s midterm preparation. 31 32

Relationships

• Mu Tianxiao — Father. Tianxiao directed Tianchen’s education, brought him to the facility where he saw Kiyotaka, and appears connected to the circumstances behind his enrollment. 1 2 4
• Ayanokouji Kiyotaka — Formerly saw him as a child in the white facility and recognized him after hearing his name in Class D. Their present interactions are polite but guarded; Tianchen understands that Kiyotaka hides his real ability. 4 23 38
• Kushida Kikyo — Initially asked Tianchen to obtain Takagahara’s contact information. After Tianchen recorded her true behavior, he blackmailed her into cooperating with his plans. 7 19 35 36
• Rokusuke Takagahara — Tianchen’s deskmate, whom he calls “Beauty Bro.” Their relationship is transactional: Takagahara tests Tianchen’s ability to gather points, sells him information, and recognizes his potential as a leader. 13 19 31
• Ryuen — A strategic adversary from Class C. Tianchen uncovered Ryuen’s use of upperclassmen, extracted 360,000 points from him, and later monitored his ambition to transfer all of Class C to Class A. 5 6 38
• Hiyori Shiina — A Class C student who bonded with Tianchen through their shared interest in mystery novels. Their relationship is one of Tianchen’s few openly genuine connections. 12 27
• Chabashira Sae — Class D’s homeroom teacher. She investigated Tianchen’s unclear school records and recruited him to help raise Class D’s points during the midterms. 26 27
• Shibata So — A friendly Class B runner who exchanged contact information with Tianchen and invited him to train together. 19
• Sakura Arisu — An old acquaintance from Class A. She knows of Tianchen’s father and Kiyotaka, and offered points in exchange for his help against the Katsuragi Faction. 43

Story Role / Major Arcs

Enrollment and Class D

Tianchen enters Kodo Ikusei High School as a First Year Class D student. He immediately notices the school’s luxury, the S System’s 100,000 starting points, and the poor discipline of his assigned class. He chooses to preserve a low profile through a deliberately timid self-introduction. 3 4

Ryuen Evidence Deal

After witnessing the confrontation involving Sudo and Ayanokouji, Tianchen follows the upperclassmen and learns they were paid by Ryuen’s Class C. He defeats them, obtains evidence, then sells Ryuen’s silence back to him for 360,000 points while testing Ryuen’s strategic capacity. 5 6

Accumulating Points

To fulfill Takagahara’s challenge of showing at least one million points, Tianchen enters the Table Tennis Club’s betting system. He manipulates his opponents’ expectations, defeats multiple seniors, and wins 500,000 points from Miyamoto Subaru. He ultimately proves he has surpassed the required balance and receives Takagahara’s contact information. 13 15 17 19

Kushida’s Exposure

Tianchen follows Kushida to the rooftop and catches her verbally attacking Horikita. When she attempts to threaten and frame him, he reveals that he has a recording device. He refuses her attempts to buy or seduce him, instead compelling her to perform an unspecified unethical task in return for his silence. 35 36

Class D Midterm Arrangement

Chabashira approaches Tianchen because of his unexplained ability and large point balance. Though he refuses to lead Class D outright, he agrees to help raise its class points during the midterms in exchange for a highly favorable points reward and confidentiality about his affairs. 26 27

Encounter with Sakura Arisu

Tianchen reunites with Sakura Arisu after investigating the second-year point standings. Arisu offers him 800,000 points and recurring monthly payments to assist her against the Katsuragi Faction during the Deserted Island Exam, while Tianchen questions her about his father and Kiyotaka. 43

Notable Quotes

“A passing Kamen Rider!” 6

“Those who hold real power and possess overwhelming strength often prefer to stay hidden behind the scenes as ‘puppeteers.’” 38

Trivia

• Tianchen frequently visits the library and enjoys both light novels and mystery novels by Keigo Higashino. 10 12
• He chose the school cafeteria’s free wild vegetable set out of curiosity rather than financial need. 10
• He coined the nickname “Beauty Bro” for Takagahara before repeatedly struggling to remember Takagahara’s actual name. 3 11