Team Kū is a group of assassins that also participated in the Ura Butou Satsujin. Their leader is Kukei, and their co-captain is Saicho.
Kukai is the leader of the Kū, and his nickname is Buddha. He has one daughter, Misora, who didn't like the fact that the Kū became an assassination group. Kukai is also referred to as Shihan Dai or Shihantai.
Saicho is a young boy who has the ability to use paper. He is the co-captain of the Kū, and is often noted as the kindest of them, especially by Fuuko. He has a heart condition that only allows him to fight for fifteen minutes. From that point on, he helped Hokage throughout the series, also creating a bond with Koganei Kaoru. Saicho believed that becoming an assassination group has ruined the Kū's name, especially Fujimaru, who loved killing and spared nobody. Even Kukei believed that Fujimaru had disgraced the Kū name. He has great difficulty in killing his opponents, as shown in a flashback.
He first appears when the Kū meet Hokage while the referees were beginning Ura Butou Satsujin. His first battle was against Recca, but lost due to his heart condition. One day, when Koganei and Saicho went into the dome after it was closed, they were caught by J-Keeper. After a small scuffle, the Joker appeared to help Saicho and Koganei. However, Joker, instead of attacking J-Keeper at first, stabbed Saicho, nearly killing the boy. Saicho was hospitalized, but there was still a chance of him dying from his wounds. He recovers, though, and appears during Koganei's battle against Joker. He reappears to fight the Hokage's opponents in the last arc, alongside the other Kū. At first, however, Recca mistook Saicho for Aoi because they look similar. Later, he, Kashamaru, Tsukishiro and Gashakura (the remainder of Uruha Ma) fight against Kadotsu, the strongest of the Ura Uruha. They were losing until Kurei came, who used the spirits of the people Kadotsu killed to fight him. After seeing Minamio amongst them, Saicho becomes upset and begs for Kurei to stop. When Kurei was about to burn him, Joker intervened and persuaded Kurei to just leave them. Afterwards, he is seen amongst the survivors group. He is last mentioned in the last chapter, listed in the latest Ura Butou Satsujin list of fighters, partnered with a person named Pochi.
Fujimaru is a skinny man, and the fastest in the Kū. He is a pervert, and enjoys killing. He lost his first (and only seen) battle against Fūko, who was extremely annoyed by his actions (stripping her) and his love for killing. Even Minamio and Daikoku, who were stated to enjoy killing by Saicho, were unnerved by Fujimaru's cruelty and passion for killing. Strangely despit being a confirmed killer(including children) he is a recurring character, appearing as late as the SODOM arc. In it he is captured by a sadistic woman who keeps him as a pet.
Minamio is a man who has very thin eyes, almost like a cat's. His body was like rubber, allowing him to take physical blows to almost zero percent damage. He faced of against Domon in Ura Butou Satsujin, but eventually lost. Afterwards, he often hangs out with the others in their rooms, and at one point compliments Yanagi on her cooking. However, in the final arc, he is killed by Kadotsu. After Saicho learns about his death from his killer, he becomes extremely upset, but continued to fight. He is last seen when Kurei turns him into a flame to fight Kadotsu, which upsets Saicho even more.
Daikoku fights using a bō that he can rotate while Daikoku is spinning it causing vibrations and gives it the power to destroy hard objects such as rocks. He usually acts as a voice of reason between the other junior team members. He is know for his swift and accurate fighting technique, but is defeated by Mikagami.