Sister

Biodata

Feature	Details
Name	Sister (妹妹)
Alias(es)	Kid; Seventeen 693
Species/Race	A mental manifestation reconstructed from Lu Xin's impression of Little Seventeen; later becomes an Ultimate 916 917
Gender	Female
Affiliation	Lu Xin's family; protector of Qinggang as the Kid 153 747
Occupation/Role	Lu Xin's companion and combat partner; wielder of wide-area mental influence 113 443
First Appearance	Earliest documented appearance: 26

Power Progression

Stage / Realm / Level	Chapter	Notes
Independent mental-monster combatant	76	Tears Head Tentacles from their hiding places, dismembers them, and bites into their core creature without Lu Xin's assistance.
Polluter and monster-controller	110 111 113	Her contamination twists a super-Level 2 monster into an abstract mass; she turns its discarded polluted section into a controllable “toy” and uses it to defeat another monster. She embraces a radiation-emitting monster to contain its mental output.
High-level contamination combat	257 262	Contaminates the Red-robed Apostle’s body despite its resistance and regeneration; ultimately converts one arm into a stitched monster she rides and commands.
Wide-area influencer	443 466	Helps lure armed forces away from Happy Town. Her power later produces mental turbulence capable of mutating people and threatening entire cities.
Ability-transfer user	563	Transfers her ability to Gecko, allowing him to escape a Spider-type ability user and counterattack.
Qinggang’s protective figure	747 896	Her presence supports Qinggang’s citizens against the pressure of the three Crimson Moons. As the “Goddess of Light,” she helps save polluted people, though her exponentially growing power becomes unstable.
Ultimate	917	Merges the distinct traits of her clones, temporarily becomes Lu Xin’s witness, heals him with Spider-type power, and shields him from overwhelming mental force.

Background / History

Sister is not the original Little Seventeen, despite sharing her appearance and carrying memories Lu Xin gave her. After Little Seventeen died in the Crimson Moon Orphanage explosion, Lu Xin retained her complete mental state and special traits; his mental power reconstructed Sister as a tangible manifestation. The orphanage children, including Little Nineteen, retained a subtle distance from her, indicating that she was not truly one of them. 916

She identifies herself as having been among the orphanage children and tells Lu Xin that she became his sister because being near him was safest. She remembers that he protected her when they escaped the orphanage, even when another side of him was consumed by anger. 764

Sister acts as a member of Lu Xin’s household alongside Mom and Father. She openly defends Lu Xin when Mom and Father criticize his mercy, and she remains deeply attached to him. 119

Appearance

Sister usually appears as a small girl with an untidy, childlike presentation. Her body can deform and separate in ways that make her physical form unstable. 76 257

• Messy black hair, often framing bright or faintly reddened eyes 358 360
• Dirty white robe or little white dress; frequently barefoot 76 360
• Can move on walls and ceilings like a spider 76
• Can split herself into independently moving pieces, then reassemble 257 490
• Has also appeared in a little red lace dress within the Museum of Calamities 451
• Her Ultimate form bears a crown of thorns, straw sandals, a golden fountain pen, and a half-finished wooden scepter 917

Personality

Sister is playful, excitable, and often treats dangerous mental monsters as toys. She laughs while dismantling monsters, enjoys difficult fights, and can become especially enthusiastic when an opponent panics or cries. 76 111 490

Her childishness is paired with fierce loyalty. She instinctively protects Lu Xin, objects when others blame him, and becomes frightened when he is in danger. 119 259 764 She is also possessive of her “toys” and reluctant to sacrifice them needlessly. 693

Although impulsive, she is capable of empathy and friendship. She forms a playful bond with Sisi and shows growing interest in social interaction beyond Lu Xin’s family. 815

Abilities & Skills

Mental Contamination

Sister’s primary ability corrupts mental bodies into distorted, stitched, or otherwise malformed forms.

• Contamination spreads from her point of contact across a target’s mental body. 110
• She can turn a contaminated section discarded by an enemy into a separate monster under her control. 111
• Her contamination can create stitched scars and deformities across massive targets. 257
• Stronger mental monsters can resist, expel, or repair her contamination. 257
• Her attempts to disrupt complex mental structures can unintentionally harm an ally, as when she worsened the Queen of Happy Town’s condition inside the light cocoon. 461

Body Separation and “Embrace”

Sister can fold, split, and extend her body into multiple autonomous portions.

• Uses separated body parts to spread her contamination over a larger surface. 257
• Entangles victims in an “embrace” that twists their bodies into grotesque shapes without necessarily causing pain. 490 491
• Moves with exceptional speed and agility, including wall-crawling and spider-like movement. 76 873
• Contained a monster’s dangerous mental radiation by separating from Lu Xin and physically embracing it. 113

Mental Influence

As the Kid, Sister can exert influence over large groups and provide psychological protection.

• Helped draw armed forces away from Happy Town without reaching her limit. 443
• Her uncontrolled surge generated mental turbulence that mutated people and produced mental monsters over a vast area. 466
• Her presence supports Qinggang’s residents against the mental pressure of the Crimson Moons. 747
• Her expanding power allows her to bring hope and relief to polluted people as the “Goddess of Light.” 896

Ability Lending and Support

Sister can share her power with others and use Spider-type traits to assist allies.

• Transfers her ability to Gecko, enabling him to break free from an enemy’s control and fight back. 563
• Uses Spider-type power to heal Lu Xin’s injuries during the final sacrifice crisis. 917
• Temporarily acts as Lu Xin’s witness after merging her clone-traits into an Ultimate form. 917

Equipment / Items

• Squeaky Chicken — a toy she carries while accompanying Lu Xin. 300 360
• Little bear — carried while teasing Father. 778
• Small backpack — frequently filled with items Sister collects. 802
• Fire Thief’s pen — stolen by Sister and used to help break a fantasy within the old Research Institute. 826

Relationships

• Lu Xin — Her “Brother,” creator, and closest attachment. He trusts her to lead fights, while she consistently protects and defends him. 113 119 764 916
• Mom — A family member who supervises and protects Sister when Lu Xin becomes dangerous; Mom also advises Lu Xin on how to use Sister’s power. 109 161
• Father — A fellow family member whom Sister provokes freely, relying on Lu Xin’s support in their arguments. 778
• Little Seventeen — The orphanage girl whose mental state and memories formed the basis for Sister’s reconstruction; Sister is not actually Little Seventeen. 916
• Sisi — A friend with whom Sister plays by poking and exchanging gestures through Sisi’s blood-red threads. 815
• Gecko — Gains Sister’s transferred power during his battle against a Spider-type ability user. 563

Story Role / Major Arcs

Early Mental-Monster Operations

Sister initially appears as Lu Xin’s unpredictable but effective partner against mental monsters. During the Core Key incident, she independently hunts Head Tentacles through a living room, forcing Lu Xin to observe rather than intervene. 76

At Satellite City’s southern wall, she contaminates a colossal mental monster and transforms its abandoned body mass into a twisted fighting construct. Lu Xin then entrusts her with the battle, allowing her to contain the monster’s final radiation burst. 110 111 113

Happy Town and the Red-robed Apostle

In Happy Town, Mom takes Sister away from Lu Xin when his shadow becomes increasingly violent. Sister worries about him and asks whether he will change. 161

Later, Sister attacks the Red-robed Apostle directly. Although the Apostle resists and repairs much of her corruption, she successfully claims one contaminated arm as a monster she can command. 257 262

The White-Dressed Girl

Sister recognizes a connection to the stitched girl in the white dress, whose body-separation ability resembles hers. Their confrontation triggers Lu Xin’s fragmented memories of the orphanage and the “three little things.” 360 361

Qinggang’s Kid

Sister becomes known as the Kid and serves as a major source of support for Qinggang. Her influence helps citizens endure the Crimson Moons, while her growing mental power allows her to participate in Qinggang’s wider efforts to protect polluted people. 747 896

Research Institute and Final Sacrifice

During the investigation of the original Crimson Moon Research Institute, Sister joins Lu Xin’s team, forms a friendship with Sisi, and steals the Fire Thief’s pen to help break an illusion. 805 815 826

The Old Director kills Sister with a mental shot, causing her body to fracture like porcelain and triggering Lu Xin’s overwhelming grief and rage. In the ensuing sacrifice crisis, her clone-traits merge; she becomes an Ultimate and protects Lu Xin as his new witness. 916 917

Notable Quotes

“Brother is not wrong...” 119

“It’s safest by your side, that’s why I became your sister...” 764

“Go quickly... The wounds are on someone else, so they won’t hurt anymore...” 917