Bourei is a hidden leaf missing-nin from Konohagakure. He later went to Kirigakure because he was despised by Konohagakure. Kirigakure accepted him and that's where he stayed for most of his life.
As a boy, Bourei usually just wandered around Konohagakure. He was usually beaten, being kicked or hit with a broom. He ran away often because of this, jumping to every building to just escape. Later, a man took him n and trained him. The man trained him about his clan and every thing else he needed to know about his clans techniques. This allowed him to become more powerful and by the time he was 10, he became a Chūnin. When he was technically a Chūnin, he was quite powerful, knowing every technique from his clan. Though he didn't care much about nature types, they were required for him to perform some of his techniques. One day, the Hokage ordered for Bourei to be killed, though his Sensei jumped in the way of the attack. Bourei killed them through unknown means, 'for he used his Clan's Kekkei Genkai. Soon after this incident, he left to Kirigakure, killing some Leaf Shinobi that stood in his way. That's where he lived for a long time since people liked a strong and scary individual.
As a boy, he usually didn't care until he was beaten. This started the hateful personality against other people in Konohagakure. When he met his sensei, he only liked him, but more than just a friend, a father. When his sensei died, he hated Konohagakure, worse then he had before. At Kirigakure, he loved it there, but only there. Those were his feelings in life. In battle, he acts if his opponents are the people who killed his sensei, so he almost goes all out sometimes.
Bourei appears as a tall and slender man with silver hair and red eyes. His silver hair covers his eyes as well. He wears a white shirt and black pants with original Shinobi boots and stockings. When he joins Kirigakure, he wears a black cloak over his clothes, and sandals like Sasuke Uchiha's.
He has amazing Taijutsu, most of his techniques are a type of fighting style or Taijutsu. He has good physical strength, while not in his Sage Transformation he is able to pick up something like a boulder, or grab a boulder out of the ground. It is like his most preferred style because of his clan, and because, he just likes it.
Like other members of his clan, Bourei possesses the ability known as Sage Transformation which allows him to use the natural energy he absorbs to transform his body at will. He can change instantly into a form that he likes in Sage Transformation and can isolate any part of the form he wants to be isolated. Also due to this, he possesses massive reserves of powerful chakra. However, because he absorbs natural energy constantly, he and his clansmen are prey to sporadic and involuntary surges of unnatural rage. If he fully transforms, Bourei gains a massive boost in overall ability and agility but loses his mind to his murderous and evil side, signified by a change in his voice and attitude. When transforming, his skin turns dark and his sclera turn black. He also gains a black stripe running from the middle of his forehead and down the bridge of his nose. In this full form, he is incredibly resilient and has significant reflexes, being able to react easily to attacks. All of these descriptions are just like Jūgo, and he looks the same in the Sage Transformation, except the fact that he has Silver Hair Spiky Hair.
Bourei was given a cursed seal, which granted him tremendous power. He bore the Cursed Seal of Earth, which is said to be equal in power to the Cursed Seal of Heaven, and both Seals are said to be the strongest amongst the ones used by it's unknown creator. When in his Level 2 form, appearance was similar to that of a dinosaur, with dark grey skin, dark black eye sclerae, yellow eye irises, a tail, dark black curved like markings under his eyes - one under each eye and two as elongated eyebrows - one above each eye. Though, he can't activate Sage Transformation with this, he is still very powerful.