Kujaku is a major antagonist in the series.
The younger twin brother of Kirin and one of the Four Guardians of Zenom Organization. He is responsible for the Reverse Kabbalah project that Zenom is conducting, and is searching for the devils. He is sadistic in nature and envious about his brother's ability to use the Cyclops third eye. He is the Demon No. 8i - Adramelech. Kujaku is an OPT but is never seen using an O-part, as he usually relies on his demon powers instead. When he was a child both he and his brother were being trained by their father to become swordsman, but Kujaku could never win during sparing matches against Kirin until he found an orb hidden in his mother's grave that contained the powers of the Adramelech and used it. After that he was easily able to beat Kirin, although once his dad realized how he won the match he was appalled and was later killed by his son.
Post time-skip he made a brief appearance in front of Kaito and Shuri when they reached the Reverse Kabbalah while they were going to free Kaito's childhood friend from being sealed up inside of the Kabbalaha. Later he fought Kirin in the mirror ruins and activated his full demon form and used an ability that causes people to go through solid objects. As Kirin began falling through the ground, he told Mei to use her cyclops eye to project him through the air. Kirin used his mouth hold his sword to slice up Kujaku's demon body. Afterwards, Kirin gave Kujaku's sword, saying it belonged to him and that their father pushed him so hard because he wanted Kujaku to be better. After seeing his name carved on the sword, Kujaku sheds tears saying "I am not alone" as Kirin walks away In Chapter 75, just as the Crew of the Ophan was about to be absorbed by Miko, Kujaku used the sword to perform the ultimate technique their father taught them to sever the tentacles and save them. Joking that Kirin was as pathetic as always, he then dies on his feet smiling.