We can identify him as the villain of the series; He is a quiet individual who turns out to be very aggressive with those who oppose him and his ideas or simply do not like them. He was raised by an alcoholic man during his childhood, until a strange man, named Jigen, bought him a large amount of money.
This Jigen guy was the leader of an organization called Kara; whose objective was the experimentation in humans with inorganic materials and energies of other dimensions. This in order to improve people’s skills and end the dominance of the shinobi or ninja.
After they experimented with him on several occasions, Kawaki receives the Kama in the shape of a black diamond -something similar to the one Boruto received in their inter-dimensional encounter- and is turned into a kind of individual different from the human being, with his nervous system and blood vessels modified with inorganic technology.
Kawaki is distinguished by being one of the few characters who have hair of two different colors, in his case, he has dark hair and the sides of his hair are blonde; He also has a few piercings in his right eyebrow and certain piercings in his ears. In addition, he has the number IX tattooed on his cheek, which identifies him as a member, intern, or ex-member of the Kara organization.