Ku: Onoki's Clone and the Coup in Iwagakure

Ku is born of a bereavement: that of Kozuchi, Onoki's grandson, killed when deserters attack Iwagakure ten years after the Fourth Great Ninja War. Retired from power, the old man unearths a jutsu and draws from it the Akuta, clay soldiers belonging to Earth Release (Doton), then conscious beings tasked with overseeing them. Ku is one of them, the only one modeled primarily on Onoki.

A Partial Clone of the Third Tsuchikage

Ku (空) was born in the anime. His profile has him appear in episode 78 of Boruto: Naruto Next Generations, credits him with only one other appearance, in the game Naruto Mobile, and cites no manga chapter. He is a synthetic human created as a partial clone of Onoki, designed to help his master replace shinobi with artificial beings, in Iwagakure as in the rest of the ninja world. His name, 空, means "sky" or "emptiness".

The anime specifies in episode 86 that Ku was modeled primarily on the Third Tsuchikage himself, the old man's DNA serving as the basis for his being. The resemblance is physical — short stature, broad face, large nose, thick eyebrows — and technical, since he inherits his model's kekkei tota. He is placed in the Fabrications species, Tsukurare (ツクラレ) in Japanese, affiliated with Iwagakure, and gives him three distinct lineages: Onoki as genetic model, a White Zetsu as genetic source, and the Iwagakure doctor as creator.

One detail of nomenclature sets him apart from his four counterparts. All the other Tsukurare appear to bear names of rocks or minerals, which it cautiously links to their manufactured nature; Ku alone receives an abstract word. The caption of an anime screenshot further specifies that it is Onoki himself who gives him this name. His status, on the profile, is that of a deceased character, and his voice actors are Subaru Kimura in Japanese and Chris Hackney in English.

The Death of Kozuchi, the Founding Event

In the anime's chronology, ten years after the Fourth Great Ninja War, Iwagakure is attacked by deserters. The assault claims several victims among the village's young people, including Kozuchi, Onoki's grandson. His profile states that he had been living with his grandfather since the latter retired, and that he died confronting a group of renegades who had come to steal Iwagakure's secrets. It is this bereavement that lies at the origin of everything that follows.

The boy's portrait fits in a few lines. Cheerful, energetic, and considered very intelligent by his grandfather, he dreamed of becoming Tsuchikage and embodied Iwagakure's Will of Stone, that way of facing every problem without ever bending. This commitment came with recklessness and an overestimation of his abilities, which caused his premature death. He looked enough like Boruto Uzumaki that an Onoki deep in delirium confused the two boys.

Onoki held himself responsible: it was he who had taught Kozuchi the Tsuchikage's ideal, that of going out to meet problems. From this remorse a precise plan is born, not to avenge the boy but to make such a death impossible — to cultivate artificial beings that would fight in place of humans. This desire became so consuming that the old man hid his work from everyone until he was certain of success.

The Akuta, Clay Soldiers Rejected by Kurotsuchi

The Akuta (芥, literally "refuse") are classified as ninjutsu, kinjutsu and Earth Release technique. Their profile traces them to a forbidden jutsu of the Land of Earth, itself inspired by a jutsu unearthed by Onoki; they are living organisms made of clay turned into weapons, a material episode 88 specifies. They travel through the ground to move around and drag their opponents into it, stretch their limbs (episode 82), know no fear, but have only a limited lifespan and intelligence.

Their weakness is their mask: destroying it kills them. The anime has them debut in episode 72. They obey instructions and communicate with the Tsukurare (episode 89), which makes them a supervised troop rather than a swarm. The inaugural demonstration nevertheless goes badly: in front of Kurotsuchi and other Iwagakure shinobi, a golem turns on its creator, his granddaughter protects him then rejects further development of the technique (episode 83).

Onoki overrides her and continues his research in secret until he obtains more docile creatures. The idea that they are devoid of will is in fact contradicted: Akkun, a small Akuta, becomes attached to Inojin Yamanaka and defies his own kind to protect him, which Kirara calls a manufacturing defect. When the artificial humans take matters into their own hands, the Akuta produced will likewise go against Onoki's orders.

The White Zetsu and Kara's Doctor

Onoki's research was advancing slowly. A scientist then approaches him with a genetic sample taken from a White Zetsu. With this material, and despite cloning techniques still in their infancy, the old man does not settle for refining his Akuta: from this collaboration are born five conscious artificial humans, able to think for themselves, meant to oversee the golems. Ku is one of the five, and the only one his profile says was modeled primarily on the Tsuchikage.

The donor was not an Iwagakure ally. His profile makes him an Outer of Kara, employed by Victor's company in the Land of Valleys, where he was working on an unauthorized project to reconstitute the God Tree from a fragment recovered during the war. He had acquired the White Zetsu's genetic material to gather data for the organization: his loyalty to Onoki was only a facade.

This doctor introduces a contradiction into the project. Unlike Onoki, he was ready for the sacrifices needed to give these soldiers a stable body. His creations remained imperfect, with a short lifespan and a structural fragility that he never knew how to correct other than by killing. He will eventually get around the flaw, but by a means that ruins the very idea of an army manufactured to spare human lives.

The Five Tsukurare and Their Internal Clock

Tsukurare (ツクラレ) designates these imperfect synthetic humans, held to be devoid of will and tasked with acting in Onoki's place to build an ideal society by replacing shinobi (episode 89). Some carry DNA anomalies that open rare nature transformations to them: Ku has the kekkei tota Dust Release (Jinton), while Sekiei gains access to Explosion Release (Bakuton), apparently acquired through the implantation of explosive clay (episode 79).

From it Sekiei draws C1, the most basic form of explosive clay, which he shapes into insects that explode; the technique's profile knows only two users: him, in the anime, and Deidara. What the five have in common lies elsewhere, in their lifespan. Cracks appear on the body when they weaken, and no fixed term is promised to them, Onoki mentioning a range going from a few months to the day after their creation.

Excess power hastens the end. Kako, who chains his Dust Release attacks without respecting the twenty seconds of rest required, dies of it (episode 87). Kirara imposes a genjutsu of total control through simple eye contact (episode 88). Kokuyo claimed he could not use jutsu and made up for it with brute strength and a pair of tonfa. Sekiei, the most emotionally sensitive of the five, drew those he cared about. All of them ended up developing a will of their own, born of the desire to live.

Son, Second, Then Rival of Onoki

Ku presents himself as Onoki's son. When Akatsuchi and five Konoha genin come to ask the retired Tsuchikage for help, it is in these terms that he reveals himself to them, son of the Third and accomplice in his plan. His profile stresses a fierce loyalty to his creator, whom he sees as a father and a master; the old man's disappearance makes him so irritable that he strikes down one of his own Akuta in anger.

He is better adjusted than his counterparts: he does not question what he is and does not despise ordinary humans. His abilities justify his rank. He holds his own against the Fourth Tsuchikage in single combat, defends himself calmly in taijutsu, wields a broad cleaver-like sword able to cut down several targets in a single blow, and, like many Iwagakure ninja, seems to specialize in Earth Release to the point of flying thanks to the Light-Weight Rock Technique.

The gap with his model comes down to one sentence his profile states bluntly: his first concern is not his creator, but the success of the goal for which he was created. Ku adopts a the-end-justifies-the-means logic, ready to disobey if he judges that Onoki's scruples are slowing the peace he aims for, sacrifices included. On learning what his species could become, he moreover begins to believe himself superior to humans.

The Coup in Iwagakure

The seizure of the village begins with a concealment. Ku, Kako and artificial soldiers abduct the Fourth Tsuchikage; to mask her absence, Kirara places Kontsuchi under genjutsu so that he answers the calls meant for the leader and claims she is on a private mission. Other officials of Iwagakure are subdued the same way. The lie holds as long as Kirara holds.

It gives way when the Tsukurare's body degrades and her illusions dissipate on the village officials. Understanding that secrecy is no longer tenable, Ku decides to take control by force and seals off Iwagakure with his army. He then learns with fury that Konohagakure has been warned of the coup. It is also he who, refusing to sacrifice an Iwagakure resident, had designated Shikadai Nara as the test subject for the heart transplant.

The break with Onoki is head-on. Brought back to the village, the old man is outraged at the measures taken and refuses the transplanting of human hearts, contrary to his goal of saving every life. Ku judges his creator too sentimental for the greater good, neutralizes him and takes full power, while having him escorted back to his quarters under Akuta guard. The underground factory where the latter were mass-produced will be destroyed by Konohamaru Sarutobi.

The Heart He Should Never Have Taken

The idea of the transplant comes from the examination of Mitsuki. The doctor finds a Curse Mark on his heart, which blocks his sensors and prevents him from uncovering the secrets of that body, but he draws a hypothesis from it: making an artificial heart from the heart of a living human would stabilize the Tsukurare and extend their lives. Ku, who is loath to kill innocents, nevertheless decides in favor of the bigger picture.

Mitsuki brings him the promised heart. Just as Ku is savoring the next step of his plan, the boy drives his hand through his chest: the container held only a cluster of his snakes. He then explains that his betrayal of Konoha was a ruse meant to sabotage the project from within. His own profile qualifies the scene, however, since Mitsuki will later admit that he genuinely considered joining the artificial humans.

Gravely wounded, Ku falls back on the Old City to be treated. The doctor tells him that the donors have escaped and that no raw material is left. Ku kills him, takes his heart and implants it in himself: the transplant gives him a body that no longer degrades and makes him impervious to pain. It comes from a man, that is to say from exactly the sacrifice the clay army was supposed to make unnecessary.

What the Five Kage Buried

Ku's end is also Onoki's. After Team 7, Sarada Uchiha included, has seriously damaged him, he launches one last Dust Release; Onoki answers it with an even more powerful attack, determined not to meet his grandson again without having atoned, and destroys his own creature. Exhausted, he reminds the genin that one can always start over after going astray, then dies. All five Tsukurare are gone by then, through exhaustion or in combat.

His funeral brings together the Five Kage and the people of Iwagakure. To preserve his reputation and acknowledge his atonement, the Kage choose to bury the truth: the version made public speaks of Iwagakure dissidents subdued by the Fourth Tsuchikage, and of an Onoki carried off by health problems. The genin who left without authorization are sent back to Konoha; those of Team 7 lose their shinobi status there, later returned on Kurotsuchi's recommendation.

The research, for its part, survives. It passes to Victor, who exploits it through his company for his own work on the God Tree. When Kurotsuchi learns that the doctor belonged to Kara, she fears her grandfather was a member of it; Hanabi Hyuga reassures her, the evidence indicating that he was used without his knowledge. Onoki's file thus joins the laboratory side of the new era, the era of thriving Scientific Ninja Tools.

Summary Table

FAQ

• Does Ku appear in the Boruto manga?
  No. His profile credits him only with the anime and the game Naruto Mobile, with a first appearance in episode 78. His whole story fits within Mitsuki's Disappearance Arc, the ninth arc of the anime, which covers episodes 71 to 92. No manga chapter mentions him.
• Why did Onoki want to replace his ninja with manufactured soldiers?
  After the deserters' attack that costs his grandson Kozuchi his life, he looks for a way to protect the peace without a single innocent dying. He unearths a jutsu and draws from it the Akuta, linked to a kinjutsu of the Land of Earth, so that they fight in place of humans. Kurotsuchi having rejected the technique after a failed demonstration, he continues alone and in secret.
• Who are the five Tsukurare?
  Ku, Kirara, Kako, Kokuyo and Sekiei. With the exception of the first, their names seem to refer to rocks or minerals, according to a cautious reading. They share a short lifespan, signaled by cracks on the body, and all five are dead, through exhaustion or in combat.
• How does Ku die?
  Mitsuki hands him a container supposed to hold a heart for transplant, which in fact holds only snakes, then pierces his chest. Ku falls back, kills the doctor and implants his heart, which gives him back a body that is intact and impervious to pain. After Team 7 has seriously damaged him, Onoki counters his last Dust Release with a more powerful attack and destroys him.
• What separates Ku from Mitsuki, the other artificial human of the arc?
  Ku is a Tsukurare made from White Zetsu genetic material, with Onoki's DNA as the model, and his body degrades for lack of a stable design. Mitsuki, a modified clone of Orochimaru, carries a Curse Mark on his heart that the Iwagakure doctor could not decipher. It is precisely that examination that puts the Tsukurare on the track of the heart transplant.
• Why does the rest of the ninja world never speak of this coup?
  Because the Five Kage preferred to keep the facts quiet, in order to protect Onoki's memory and honor his atonement. The official statement merely mentions dissidents put down by Iwagakure's leader, and a former Tsuchikage supposedly carried off by health troubles. The research, for its part, was recovered by Victor for his own work on the God Tree.

In summary

Ku turns the project that gave him life against its own purpose. Designed so that no human would ever have to die in combat again, he kills the Iwagakure doctor in order to implant his heart; Onoki answers his last Dust Release with a more powerful attack, destroys his creature, then passes away.