Kū

Kū dressed in the green-and-red robe worn by Iwagakure's leading figures, with a green flak jacket beneath it. Modelled on the Third Tsuchikage, he was short, his shaggy brown hair falling past his chin to hide the left eye while the rest reached the middle of his back. He shared Ōnoki's broad face, prominent nose, and thick brows.

A guarded, single-minded figure, Kū pursued his purpose without flinching, all in the name of reshaping the world into something peaceful. He revered Ōnoki as both father and master and grew agitated when the old man vanished, once striking down one of his own Akuta in frustration. Steadier than the other artificial humans, he neither doubted his own nature nor sneered at ordinary people, at least at first.

Even so, the mission always came before the man. Kū embraced an ends-justify-the-means outlook, ready to defy Ōnoki and spend lives if he judged it necessary for peace, while still wishing his creator no harm. As he glimpsed what his kind might one day become, arrogance crept in, and he began to see himself as superior to humans and as the true future of the world.

Kū owed his existence to tragedy. After missing-nin raided Iwagakure and killed a number of its young, among them his grandson Kozuchi, the retired Ōnoki set out to build the Akuta as replacement soldiers. A scientist supplied genetic material from a White Zetsu, and with it Ōnoki produced five self-aware artificial humans, Kū chief among them and grown mainly from the Tsuchikage's own DNA. That heritage made him a formidable ninja, able to stand against the Fourth Tsuchikage one-on-one. He commanded the advanced Dust Release, fusing earth, fire, and wind to disintegrate his targets, layered in Earth Release for flight and stone prisons, and could raise Akuta golems, all backed by sharp taijutsu, a heavy cleaver, raw strength, and speed.

Working from the shadows, Kū joined Kirara and Kakō at an Akuta facility, abducted Kurotsuchi, then cornered Akatsuchi and a group of Konoha genin, revealing himself as Ōnoki's supposed son and ally. He told the boy Mitsuki that his unusual body held the key to completing the plan. As his own frame began breaking down like the others', Kū concluded that transplanting a human heart could stabilise the artificials, and, unwilling to spend an Iwa life, chose Shikadai as the test subject. With his scheme exposed, he threw the village into lockdown and, when Ōnoki objected to the bloodshed, incapacitated his creator and seized full control.

Mitsuki then arrived offering a donor heart, only to drive his hand through Kū's chest, the organ a mass of snakes and his defection a ruse to gut the plot from within. Gravely wounded, Kū killed his own doctor for a replacement heart and confronted Team 7 one last time. As his Dust Release bore down, Ōnoki, resolved to atone before facing his lost grandson again, answered with an even greater blast that finally destroyed him.