Kū (also known as Lord Kū) is an antagonist from the anime series Boruto: Naruto Next Generations. Kū is the main antagonist of the Mitsuki Disappearance Arc.
After Iwagakure was attacked by rogue ninjas, Ōnoki was emotionally affected by this loss as he witnesses his grandson, Kozuchi, fall. Ōnoki started to work on creating the Akuta. A scientist approaches Ōnoki with a genetic sample from a White Zetsu (previously from the Fourth Great Ninja War). Ōnoki was not only thinking about the Akuta. He also creates five artificial human-beings that also included Kū.
He is very perpetrated to his ambitions and will complete his orders without qualm. He is shown to be loyal to lord Ōnoki. At the same time, he refuses to go against Ōnoki's goal of the least amount of bloodshed possible. Unlike the other artificial humans, Kū is shown more well-adjusted as a human.
Even though he's loyal to Ōnoki, his first and most important concern is the success of Ōnoki's goal for which he was created. Kū then adopted an "ends justify the means" mentality, willing to go against Ōnoki's orders, including a willingness to sacrifice innocent lives, though had no ill-will towards Ōnoki and wishes him to remain safe. At the same time, in learning the potential evolution of his being, Kū became more full of himself, feeling superior to humans and the true future of the Shinobi World. Kū holds a deep grudge against Mitsuki after he attacks him from behind and gave him a fake heart using snakes.
Kū, along with Kakō appears to be some type of research facility in the making of Akuta. Kū, Kakō, and some of his artificial soldiers then kidnaps the Fourth Tsuchikage, Kurotsuchi. Akatsuchi and five Konoha genin seeks Ōnoki for help in finding their missing teammate Mitsuki, Kū surrounded the genins with his Akuta. He then discovered to the captured foes that he is Ōnoki's son and is working with him.
After Ōnoki has been taken, Kū had his soldiers reinforce more Akuta while insisting to keep their actions unrevealed. He finally meets with Mitsuki. The boy asked about the essence of free will. Kū states that he could not answer the question as an artificial human like Mitsuki and that Orochimaru was the best chance of him getting an answer due to him being the creator of Mitsuki. He notes that Mitsuki betraying Konohagakure is common as a sign of maturing. He went on to insist that the unique nature of Mitsuki's being would be instrumental in completing the Third Tsuchikage's plans to ensure lasting peace through the Akuta.
Kū spoke to his scientist about the progress on studying Mitsuki's improved body as his body began crumbling. The scientist explains that adding an actual human's heart into an artificial human would likely maintain the artificial humans. Kū decided to look at the bigger picture on continue his mission of protecting all and proceeds to make the sacrifice despite not wanting to harm the innocent people. He told the scientist to test the theory with Shikadai which then failed.
Later on, the village was on a lockdown by Kū's army. Mitsuki makes it at the Iwa main building with a transplant heart for Kū. Sarada and Boruto intervenes. As they trying to convince Mitsuki not to listen to Kū, Kū mobilizes the two genin. Once Kū had received the new heart, Kū began celebrating the next stage. Mitsuki then attacks Kū from behind. He revealed that the transplant heart was was disguised as snakes and his defection of Konoha was a plan to let Mitsuki destroy the enemy's plans from inside. While seriously injured, an enraged Kū refuses to forgive Mitsuki.
Kū flees in order to patch up his wounds and decaying body. Once he makes it back, the doctor informed Kū the donors had fled and there weren't any raw materials for the artificial heart. Kū then murders the doctor, obtaining his heart and transplanting it. After recovering, he is confronted by Boruto, Sarada, and Mitsuki.
As Kū began to recover his power, Ōnoki attempts to reason with Kū again on how he's going against the original path. Kū however revolts that his hatred was inherited from Ōnoki and attacked the group. Sarada rescues everyone by breaking through the ground. Team 7 managed to seriously injure Kū by taking his heart out. Kū then tries to finish everyone on the group, only for Ōnoki to finish him off with a much powerful one, in order to repent.
Kū wears a green and red robe like Ōnoki. Underneath, he wears a green flack jacket. Like his template, he is a short man with shaggy brown hair. Like Ōnoki, he has a broad face with a large nose and thick eyebrows.