Yan Si

Biodata

Feature	Value
Name	Yan Si (言祀)
Alias(es)	“Meat Bun” and “Bun,” used by Satoru Gojo 22
Species/Race	Human; transmigrator 2
Gender	Male 11
Date of Birth	April 4, 1990, according to his enrollment file 16
Age	Fourteen before his fifteenth birthday; earlier descriptions call him fifteen 2 3 16
Nationality	Chinese 22
Affiliation	Tokyo Jujutsu High, incoming first-year class 16
Occupation/Role	Jujutsu sorcerer and student; formerly a mathematically gifted university student 1 16
Status	Alive in his second life; died in his original world 1 49
First Appearance	Chapter 1, “Haha, Off to Enjoy the Good Life” 1

Power Progression

Stage / Realm / Level	Chapter	Notes
System-bound beginner	2	Chooses the sorcerer path. Starts with 0 cursed energy, 15 strength, 3 physical strength, and 2 speed; retains hundredfold sensitivity and his cursed-spirit-attracting constitution.
Cursed energy: 0 → 9	4	Spends 18 pain points, exceeding the six-point threshold for seeing cursed spirits. Uses cursed-energy-coated precision strikes to defeat a Grade 4–borderline Grade 3 spirit.
Speed: 2 → 7	5	Spends ten points during a Grade 2 spirit’s attack, gaining enough speed to evade its next strike despite severe injuries.
Reverse Cursed Technique; system assessment: Grade 2–Grade 1 sorcerer	6	Converts near-fatal injuries into points and spends 253 on healing and stat upgrades. The resulting panel records 48 cursed energy, 23 strength, 16 speed, and 3 constitution. Regenerates his severed lower leg and kills the Grade 2 spirit.
Reverse Cursed Technique output confirmed	15	Established as capable of healing other people, making him a rare and valuable prospect for Jujutsu High.
Pain-sharing ability acquired	19	Purchases “How Many Floors Can a Bag of Rice Climb?” for 50 points. Gains adjustable, unlimited-range pain sharing with manual or conditional activation.

Background / History

Yan Si grew up in the Yan family’s wealthy ancestral household in China. Both parents suffered from mental illness, and his childhood included violence and food deprivation. His mother left the vermilion mark between his brows by stabbing him with glass during an episode; he remembered the hug preceding the injury as more precious than the pain 3 7 9.

His father, Yan Zeming, was a brilliant mathematician nominated for the Fields Medal. The family’s longtime butler, Uncle Li, learned not to challenge the family’s perceptions after Yan Zeming jumped from a second-floor window to prove he could fly. Both of Yan Si’s parents were dead by the time of his second life 7.

In his original world, Yan Si became a university student with exceptional mathematical ability. He died after slipping on a rotten banana in a stairwell and falling several floors, with his injuries compounded by a pre-existing heart condition. He awoke in a younger body in the ancestral home on March 7, 2005 1.

The system explained that his familiar surroundings were a beginner benefit, not evidence that he had simply returned to the past. Offered either an ordinary, healthy life or a dangerous career in jujutsu, he chose the latter, treating his second life as an opportunity to escape his previous routine 2.

Appearance

Yan Si has an unusually beautiful, androgynous appearance that repeatedly distracts others and leads the young Kasumi Miwa to mistake him for a woman 1 10 11 30.

• Hair: Long black hair reaching his waist, with slightly curled ends; often worn in a low ponytail 3 10.
• Eyes: Deep purple, with slightly upturned outer corners and an often-smiling expression 1 11.
• Forehead mark: A vivid vermilion spot centered between his brows, originating from his mother’s glass-inflicted injury rather than a natural mole 1 3.
• Build: Approximately 173 centimeters tall when first examining his new body, with broad shoulders, a narrow waist, and a thin teenage frame 1.
• Complexion: Exceptionally pale skin, visible bluish veins at his wrists, and long, thick eyelashes 1 11.
• Clothing: Wears black outdoor jackets and uses sunglasses and earplugs to reduce sensory overload in Tokyo 8 46.

Personality

Yan Si is sardonic, vain, restless, and strongly attracted to novelty. He openly praises his own beauty, turns ordinary conversations into absurd arguments, and treats dangerous encounters as entertainment. His willingness to become a sorcerer comes from valuing experience over a safe repetition of his former life 2 14 17 30.

His mathematical instincts extend to the system: he compares prices, evaluates mission risks, identifies diminishing returns, and treats suffering as an investment. This pragmatism coexists with extreme recklessness toward his own body. Reverse Cursed Technique encourages him to accept injuries—and sometimes avoid dodging simply because it feels like too much effort 3 4 18 29.

He is deliberately provocative and often disregards other people’s boundaries. He brutally retaliates against an office worker who collides with him, needles assistant supervisor Henshita Tsugina about his private life, and manipulates Gojo’s guilt through a prolonged performance of helplessness 8 41 42 46.

His apparent indifference does not exclude care. He rescues Kasumi, treats her wounds gently, saves cursed spirits for Geto, and pays for Tsugina’s meal. Affection between Kasumi and her mother exposes his discomfort with ordinary family tenderness, while his private thoughts reveal concern about Kasumi’s tragic future and Geto’s eventual defection 10 11 17 37 49.

Abilities & Skills

Pain-Point System

Yan Si’s bound system converts suffering into currency for attributes, abilities, and items 2 5 6.

• Primary income: Pain he personally experiences; intense negative physical or emotional stimuli can also generate points 5 6.
• Secondary income: Inflicting pain on enemies provides comparatively small rewards; completed missions award separate fixed rewards 6.
• Attribute upgrades: Two points purchase one stat point 2.
• Diminishing returns: Repeatedly aggravating the same wound yields progressively fewer points 4.
• Recovery cost: Healing removes injuries but not the exhaustion, cold sweat, numbness, or lingering sensations associated with repeated pain farming 18.

His assigned objectives include reaching Japan, joining Jujutsu High, becoming a curse user, causing important characters pain, and ultimately defeating peak Sukuna. The curse-user objective is a mission, not an established affiliation 3.

Hundredfold Senses and Pain Immunity

His five senses are enhanced a hundredfold, providing exceptional perception while making ordinary discomfort and injuries intensely painful 2 4 8.

• Detects a cursed spirit’s presence through a “sixth sense” even before acquiring enough cursed energy to see it 4.
• Tracks movement in extreme detail and anticipates attack trajectories 4 9.
• Locates concealed people through faint breathing and footsteps 14 15.
• Suffers sensory overload in busy streets; cursed-spirit shrieks can make his ears bleed 8 9.
• Pain Immunity prevents pain-induced death and forcibly stabilizes him when agony threatens shock; it does not prevent him from feeling pain 2 4 6.

Cursed-Spirit Attraction

His constitution compulsively draws nearby cursed spirits toward him while intensifying their hostility 4 15.

• The system displays the effect as “Cursed spirit’s desire to attack you: 150%” 4.
• Draws four spirits, including a Grade 1, from across much of Hachioji 15.
• Affects Geto’s stored and controlled spirits, although Geto can restrain them 12 16.
• Can simplify locating mission targets, prompting Gojo to call him a potential “Cursed Spirit Radar” 22.
• Makes him a perceived public-safety risk and contributes directly to the higher-ups’ assassination order 15.

Cursed Energy

Yan Si has no naturally generated cursed energy because he is a transmigrator; his supply is purchased and generated by the system 2 38.

• Reinforces punches and fuels Reverse Cursed Technique 4 6.
• Reaches a documented total of 48 after his first major upgrade 6.
• Produces an irregular output waveform during class testing because of its system-generated origin 38.
• Conceals that explanation from Yaga, attributing the fluctuations to his unusual constitution instead 38.

Reverse Cursed Technique

Purchased for 199 points during his first Grade 2 battle, Reverse Cursed Technique allows Yan Si to recover from otherwise fatal damage 2 6.

• Regenerates his lower right leg and repairs broken ribs, a punctured lung, and heart damage 6.
• Closes the heart wound within three-tenths of a second 6.
• Heals ordinary wounds within seconds without leaving scars 18.
• Can be output to heal others, a rare ability recognized by the jujutsu authorities 15.
• Does not improve his documented constitution of 3: his own punches can still break his hand, requiring further healing 6.
• Is not protection against instant death; Yan Si’s confidence in surviving assassination explicitly depends on not being killed immediately 15.

“How Many Floors Can a Bag of Rice Climb?”

This purchased ability shares a selected proportion of Yan Si’s pain with a designated target 19.

• Begins with a 10% sharing rate, which can be raised to 100% 19.
• Has no distance limit 19.
• Supports manual activation or preset triggering conditions 19.
• Is bought for 50 points, reducing his balance from 306 to 256 19.
• Appeals to him as retaliation: rather than merely escape suffering, he wants whoever hurts him to experience it alongside him 19.

Close-Quarters Combat and Evasion

Yan Si combines exceptional sensory anticipation with fast, precise punches and basic knife strikes 4 14 30.

• Targets weak points rather than relying solely on brute force 4.
• Kills one Grade 1, two Grade 3, and one Grade 4 spirit in under three minutes with his boning knife 14.
• Commonly uses an all-offense style, healing damage instead of defending 14 28.
• Receives “Excellent” on Yaga’s evasion assessment, proving he can dodge effectively when required 30.
• Maintains his balance on Gojo’s shoulders through sprinting, abrupt stops, sharp turns, and jumps 44 45.
• Enhanced perception alone cannot guarantee evasion: the first Grade 2 spirit overwhelms him through speed and bodily damage 5 6.

Academic Ability and Languages

Yan Si is a mathematical prodigy with accelerated schooling and strong recall 2 16 37.

• Skipped three grades, completed high school, and earned admission to a prestigious university 16.
• Qualified for university without an entrance examination through mathematics competition results 2.
• Reproduces Yaga’s cursed-energy explanation almost verbatim despite appearing inattentive 37.
• Reads Japanese and speaks a deliberately learned, fluent Kansai dialect, chosen partly to annoy others 8 32.

Equipment / Weapons / Items

• Black boning knife: Special cursed tool purchased during Kasumi’s rescue. Bypasses cursed-energy defenses to attack the target’s soul/body directly. Requires the user’s own blood sacrifice and binds to them for life; each use has a 60% chance of also affecting the wielder 10.
• System storage: Used to put away the boning knife after combat 10.
• Fruit knife: His initial weapon and early means of earning pain points; breaks during the Grade 2 battle 1 4 6.
• Sunglasses and earplugs: Reduce the discomfort caused by Tokyo’s intense sensory environment 8.
• High-powered flashlights: Purchased to locate and startle assistant supervisors inside a Curtain 14.

Relationships

• Suguru Geto — Close companion and mission partner. His constant presence prevents an assassin from approaching Yan Si; later he provides hair ties, tends injuries, and prepares class notes for him. Yan Si reciprocates through saved cursed spirits, sightseeing, and a souvenir charm, while teasing him as “Mommy Geto” 15 17 20 30 41 49.
• Satoru Gojo — Classmate, kindred troublemaker, and playful rival. They exchange “Meat Bun” and “White-Haired Cat,” encourage each other’s defiance, and turn an accidental injury into an elaborate shoulder-riding prank. Gojo becomes fascinated by Yan Si’s fearless enjoyment of danger 22 31 41 42 45.
• Shoko Ieiri — Classmate and fellow Reverse Cursed Technique user. She exchanges snacks and dry insults with him, recognizes his manipulation of Gojo, and refuses invitations to join his stunts 22 26 39 41 44 46.
• Masamichi Yaga — Homeroom teacher. Recognizes Yan Si’s talent but sets explicit restrictions on his injury-taking habits and regards his disregard for rules as dangerous 25 29 30 49.
• Mei Mei — Upperclassman who compliments his appearance and later warns him to take care of himself and clean up. The reason for her warning remains implied rather than confirmed 16 34.
• Kasumi Miwa — Rescued from a Grade 3 spirit. Yan Si bandages her neck and carries her home; recognizing her name prompts concern about her future connection to Mechamaru 10 11.
• Yoshiko — Kasumi’s mother. Thanks him with tempura; her affectionate response to Kasumi unsettles him by contrasting with his own childhood 11.
• Uncle Li / Li Shu — Longtime Yan family butler. Worries about his safety and mental health and receives his travel and inheritance instructions 7.
• Yan Zeming — Deceased father, an exceptional mathematician whose mental illness shaped the household’s history 7.
• Mother — Deceased, abusive parent whose appearance and intelligence Yan Si inherited. His attachment to her rare affection persists despite the violence 3 7.
• Hatoyama Jushō — Tokyo Jujutsu High principal who approves his recruitment despite the risks of his constitution 15 16.
• Henshita Tsugina — Assistant supervisor who transports him on missions. Yan Si relentlessly teases him during the drive but later pays for his ramen 46 47 49.
• The System — Bound source of his missions, purchased abilities, and pain rewards. Their exchanges alternate between practical questions, insults, flattery, and sarcastic banter 2 3 19.

Story Role / Major Arcs

Choosing Jujutsu and Acquiring Healing

Yan Si’s first encounters establish the system’s central trade-off: suffering creates purchasing power, but his body remains fragile. A Grade 2 attack forces his first major breakthrough, as he buys Reverse Cursed Technique and turns a nearly fatal defeat into victory 4 5 6.

Arrival in Japan and Kasumi’s Rescue

He leaves China to avoid its lineage-focused jujutsu institutions and pursue training in Japan, arriving in Tokyo on March 10, 2005. A child’s screams lead him to Kasumi Miwa, whom he rescues with his newly purchased boning knife. After returning her home, he leaves to confront the spirits gathering around him 7 8 9 10 11.

Geto and the Enrollment Dispute

Geto discovers Yan Si while investigating the convergence of cursed spirits. Yan Si’s subsequent combat display brings him to the authorities’ attention, but his attraction effect makes the higher-ups seek his assassination. Geto’s proximity blocks the attempt, and the authorities instead pursue recruitment; Tokyo accepts him after Kyoto’s established families reject the risk 12 14 15 16.

First-Year Class and Defiance of Authority

With Gojo and Shoko’s arrival, Yan Si becomes part of an exceptionally talented but difficult first-year class. His excellent evasion result and academic recall contrast with his refusal to take discipline seriously. By his unauthorized afternoon departure, Yaga’s concern has shifted beyond missed lessons to whether someone so powerful and unpredictable can be governed by the school’s rules 22 25 30 37 46 49.

Notable Quotes

“I know. I just like talking trash. Leave me alone.” 9

“Pretty good acting, huh? Want to praise me?” 42

“Good kitty! This is fun. Do it again~” 45

Trivia

• His April 4 birthday is linked in the text to Japanese wordplay connecting two readings of “four” with “happiness” 16.
• He wants Cursed Spirit Manipulation, priced at 888 points, but has not purchased it in the supplied chapters. He rejects pursuing Limitless because obtaining the accompanying Six Eyes would attract dangerous attention 9.
• Enjoys caramel pudding and plays Tetris while anticipating his trip to Japan 7 17.
• Has a seafood allergy but treats its symptoms casually and jokes that he could test whether seafood is genuine 12 39.
• Nicknames Geto’s flying cursed spirit “Duck Express” or “Duck No. 3” 20.