Fuuinjutsu

This unnamed Fuuinjutsu technique attached the Shukaku Ichibi to Gaara's unborn body. Shukaku was attached to two Sand ninja previously by Chiyo, presumably using this same technique. To attach the demon, the technique must bring the two beings into synch, both bijuu and human. As a consequence of the attachment, Gaara's mother Karura lost her life. Akatsuki has termed the attachment of demons to an individual and the resulting loss of life a "Jinchuuriki," literally "the power of human sacrifice." Such a technique will grant the human portions of the demons power. Kazekage hoped this would create an ultimate ninja, who would have near unlimited chakra from the demon. As a result of Shukaku's attachment, the demon protects Gaara with nearby sand.