- Name: Iron Body
- Type: Ninjutsu, Hiden Jutsu, No rank, Supplementary
- Users: Kakuzu
This technique transforms the user's body to something similar of a rag-doll, held together by hundreds of thick black threads. Kakuzu is able to manipulate these threads for many purposes. He is capable of detaching his limbs and manipulating them for long range attacks, as well as sewing up any injuries that he may suffer. He can also use these threads to sew up damaged bodies of others, as demonstrated with Deidara's arms and Hidan's head.
The most significant point of these threads are that they grant Kakuzu a form of immortality (though he declines to think of it that way). Aside from sewing up his injuries, he can use the threads to tear into a victim's body and steal their still functioning organs and integrating them into his own body, extending his life. Kakuzu usually uses this method to steal hearts from powerful shinobi, able to store up to five hearts at any given time (meaning all five hearts must stop functioning in order for Kakuzu to die).
These hearts Kakuzu took from others are stored in various animal masks sewn onto his back, granting him vast amounts of chakra and numerous elemental affinities. He can detach these masks and have them take on a body of their own, composed entirely of threads. These masks are capable of attacking separately, unleashing devastating blasts of elemental chakra.
These threads can also compact together to form a spider-like body around Kakuzu, allowing him to fuse the attacks of his masks together in order to increase his attacking power.