More than 15 years from his debut in Naruto Chapter 312, Kakuzu remains one of the series’ most memorable and terrifying villains. Identified through his signature technique, the kinjutsu Earth Grudge Fear, Kakuzu's design and personality have inspired both admiration and speculation from fans.
Many of these quirks, such as Kakuzu's singular obsession with money, have never been fully explained. While much remains shrouded in mystery, looking into Kakuzu's backstory in Naruto and his inspirations from external sources offer insight and raise new questions about this compelling antagonist and his signature kinjutsu, Earth Grudge Fear.
Kakuzu's Design Was Inspired by Mobile Suit Gundam
Beginning with the kinjutsu's name, Earth Grudge Fear, Kakuzu is a web of references and callbacks. In the Naruto databook, the pronunciation of its kanji "Jiongu," is a reference to Mobile Suit Gundam. The Zeong or "Jiongu" was a class of mecha that used control wires to detach its own limbs for attacks. In Naruto, the kanji themselves 地怨虞” bundle in additional meanings from folklore and contemporary culture. Of these, the most significant is the second character 怨 ("on"), the literal meaning of which "grudge" coincides with the celebrated 2002 Japanese supernatural horror film "Ju-on" ("The Grudge"), and sheds light on both the character and the jutsu's ultimate design.
The Patchwork 'Grudge'
In these films, inspired by the onryo of Japanese folklore, a vengeful spirit returns to terrorize the living for its mistreatment and death, becoming a living curse -- a motif with clear parallels to Kakuzu's backstory. Specifically, in Naruto, the events of Kakuzu's life, from his wrongful imprisonment and torture, his theft and usage of Earth Grudge Fear to cannibalize his village elders in revenge, his life as a bounty hunter, and his eventual recruitment into the Akatsuki weave together disparate narratives into a single story. Similar to the explicit function of Earth Grudge Fear in Naruto, the character's inspirations and design also "stitch" together unlike elements of science fiction, horror, and folklore to form its own unforgettable patchwork monster.
Earth Grudge Fear Is Medical Jutsu Gone Horribly Wrong
In Naruto, most kinjutsu are only radical enhancements of existing jutsu. As an example, the kinjutsu Akatsuki member Deidara stole from Iwakagure is not the ability to make his signature explosive clay, but rather implanting the strange mouths on his hands and chest that enhance that ability. This dovetails with speculation that Kakuzu was in his past, a medical ninja. The genesis of "Earth Grudge Fear" then, could have been a forbidden form of medical ninjutsu that allowed its users to use chakra like a medical suture. This would offer miraculous healing potential by preserving individual chakra natures and special abilities. This also would explain his knowledge of the kinjutsu while imprisoned in Takigakure, and his later use of the same kinjutsu on Hidan and Deidara, in the Akatsuki. Yet for the true form of "Earth Grudge Fear", Kakuzu twists this original, benign function and harvests victims' hearts, grafting them into his own body. This in turn allows Kakuzu to preserve their chakra natures as masked constructs which aid him in battle.
Pondering the cost of these transgressions brings up Kakuzu's most enigmatic characteristic, his greed. To date, no answer has been given in Naruto for Kakuzu's avarice, and many fans have lamented this quirk's apparent “pointlessness." Nevertheless, it is possible to explain Kakuzu's greed in terms of his backstory and "Earth Grudge Fear". The basic idea is that Kakuzu in fact does not want money, but rather that he needs it. This is based on the presumption that all kinjutsu in Naruto have a price, and for medical or life-giving kinjutsu in particular, such as Creation Rebirth, Outer Path — Samsara of Heavenly Life Technique, or Chiyo’s Kishotensei, the user gives up their life. In this theory, Earth Grudge Fear follows this example, but with another twist, one that follows from Kakuzu's most famous quote.
'Cash Rules Everything Around Me'
In Naruto Chapter 314, Kakuzu matter-of-factly told his partner Hidan, "Hell runs on money." At its most basic level, this theory takes Kakuzu at his word, that remarkably and unlike other kinjutsu, Earth Grudge Fear allows its users to literally pay their way out of its costs. This explains the desperation and miserliness of Kakuzu's greed, and provides practical motivation for his need to consume hearts: he must do it to stay ahead of his debt. Essentially then, Kakuzu is an indentured servant trapped inside a monstrous patchwork body he must replenish with human hearts, all the while scrambling to pay his kinjutsu's lease. Though outlandish, this theory places every detail of Kakuzu's life and personality, from his battle with Hashirama, mistreatment by Takigakure, his grisly revenge, and his mercenary partnership with the Akatsuki in a new, purposeful context.
Lastly, this theory aligns Kakuzu with Naruto's principal theme, the futility of hatred, with "Earth Grudge Fear" serving as a literal warning. Betrayed, Kakuzu sold his soul for vengeance but must live on, cannibalizing others to balance the debt his own "grudge" has incurred, the stitches disfiguring his body a constant reminder of this eternal bondage to hatred.
