When Sogetsu and Kazuki were babies, they were found under the bridge. He don't know if they are really connected, but they become the ninja of the Kazama family. He was ordered to execute a powerful fire demon named Enja. When he searches for demons and eventually meets him. However, Enja is too strong for Kazuki, but his younger sister Hazuki saves him and Sogetsu by sealing the devils in each of their brother's almighty weapons.
After learning that Hazuki was kidnapped by Amakusa, Kazuki decided to abandon the clan to rescue her, basically become a nukenin. His clan did not tolerate the traitors, they sent his brother Sogetsu to assassinate him. Two dates at the Amakusa castle. There, Kazuki defeated Amakusa and saved his sister. On the other hand, Sogetsu stayed to fight Zankuro. After returning his death to his family, Kazuki and Hazuki continued to escape and live a carefree life.
In the 64 series, made him pursue Yuga first to retaliate against the death of his adoptive father. In the ending, he still needs to save a captured Hazuki. In order to gain the strength needed to save his sister, and his unscrupulous use of the power of the soul sealed in his sword, and overwhelmed. He successfully saved Hazuki and suppressed Enja. Since then, he has chosen to live in peace with Hazuki.
Kazuki lives happily in a village with Hazuki. When he found the injury, she begged him to help a girl who was taken away. He left to perform his sister's request. However, he successfully eliminated his position with Hazuki's Nukenin and reintegrated into the team through Sogetsu's involvement.
Kazuki is a hot-headed and rambunctious youth, lacking the emotional restraint common to other ninja characters. He often goes with his gut feelings, choosing to ignore the consequences of his actions until he's faced with it. He cares deeply for his siblings, though he often dotes on Hazuki.