Ikkaku

Ikkaku first came into being in the waning days of the Sage of the 8 Paths who used his Creation of All Things ability to Separate Satan's Chakura and divide it into ten separate constructs in order to ensure that it would never resurface after his death.[3][4] Some time after being created, the Sage sat down with all the young tailed beasts and told them that they would always be together even when separated, and that one day they would become one entity again with different names as well as forms than they did then when the time came for them to understand what true power is.[5]

Citizens of Sunagakure came to believe that Shukaku was a living ghost (生霊, ikiryō) of a corrupted Suna priest, and was originally sealed inside a tea kettle.

Shukaku had two jinchūriki in the past, one of which inspired the Third Kazekage to create the Iron Sand technique. Ikkaku was eventually removed from their bodies, resulting in their deaths.

Legend of Kyoto
When Karura became pregnant with Gaara, her husband, the Fourth Kazekage, had Chiyo to seal Shukaku into Gaara and Ikkaku into Kyoto while he was still in the womb, because of his Four children, Gaara was the only compatible one with the beast. Before Karura died from a premature childbirth, she passionately told her son that she would protect him and according to her husband, her love seeped into the sand. However, Kyoto couldn't properly control Ikkaku's powers, killing or injuring several of Suna's shinobi and citizens. Deemed a failure, the Fourth Kazekage chose to test his son, ordering Yashamaru to assassinate him and also tell him that his mother never loved him, and that she was used as a human sacrifice for the sealing process. Gaara failed the test, fully releasing the rampaging Shakaku and Kyoto was felt betrayed, Unleashing the Destructive Ikkaku. to which the Fourth eventually used his Gold Dust to subdue the Ikkaku and Shakaku.

Users
Kyoto