Dead Demon Consuming Seal

The Dead Demon Consuming Seal is a seal developed by the Uzumaki clan. It invokes the power of a spectral entity known as the that can only be seen when it grasps one's soul. Once called upon, the Shinigami hovers behind the user and wraps its left arm with prayer beads, uttering some unintelligible chanting, and after some time a cursed seal appears on its arm. The soul of the summoner is then partially separated from the body and restrained by the Shinigami's hair as it thrusts its arm into the user's chest to grab the soul of its target. At the user's command, the Shinigami then performs the sealing by dragging the target's soul into the user whose stomach is branded with the seal's mark. However, the sealing is double-edged as the user's soul is devoured by the Shinigami along with the target's, both souls trapped for all eternity within the fiend's stomach.

It is also possible for the user to seal multiple targets through the use of shadow clones. The methods of sealing vary, Hiruzen needing to get close to his targets in order to perform the sealing, while Minato was able to extend the Shinigami's hand to grab Kurama.

In the two known cases where the Dead Demon Consuming Seal was used, Minato and his predecessor Hiruzen are unable to completely take their respective opponents' entire souls with them. In Minato's case, intending to seal Kurama in Naruto, he had the Shinigami devour Kurama's Yin chakra so that the weakened Tailed Beast's composition would be purely Yang. In Hiruzen's case, he was forced to take a part of Orochimaru's soul within his arms, revealing that the body parts dealt in such a manner suffer from necrosis and paralysis, causing the target extreme pain that worsens over time. Though Orochimaru undid the damage by entering a new host with working arms, he remained unable to form hand seals properly, and therefore could not use more intricate techniques such as Summoning: Impure World Reincarnation until he retrieved his arms' soul.

Countering
Due to the nature of the Dead Demon Consuming Seal, those whose souls are sealed away by it cannot be reincarnated. However, there is a way to break the seal. The procedure involves invoking the Shinigami using a mask from the Uzumaki Clan's Mask Storage Temple. From there, the act of the deed is potentially fatal as the summoner cuts the Shinigami's stomach to release the trapped souls. However this wound to the Shinigami is reflected on the invoker's body. The souls are then released from the Shinigami's stomach.

Trivia

 * During his discussion with Kushina on how to deal with the Nine-Tails, Minato stated: What he meant by this is unclear as the Hokage did not elaborate.
 * In the manga and anime, Hiruzen calls this technique by its full name, . The databook entry for this technique drops the "Sealing Technique" part.
 * Though unconfirmed, it is likely Kushina Uzumaki taught this jutsu amongst other Uzumaki clan fūinjutsu to Minato.