Hiruko is the primary antagonist of the animated film Naruto Shippūden: The Will of Fire. He is a former shinobi from Konohagakure, the Hidden Leaf Village, who became a rogue ninja, or missing-nin, after his secret research was discovered. He was once a contemporary and friend of the legendary Sannin, Jiraiya, Tsunade, and Orochimaru. Unlike his talented peers, Hiruko was born with no natural special abilities, and this perceived inferiority fostered a deep sense of resentment within him. This insecurity drove his obsession to become a powerful shinobi by any means necessary.

Hiruko's primary motivation is to overcome his innate weaknesses and achieve ultimate power, seeking to surpass his former friends. To accomplish this, he developed a forbidden jutsu known as the Chimera Technique, or Kigaro no Jutsu, which allows him to fuse the bodies of other ninja with his own. Through this technique, he can forcibly acquire and wield their Kekkei Genkai, the unique bloodline abilities that are typically hereditary. His ultimate goal is to obtain five different Kekkei Genkai to become an immortal and invincible being, which he believes will allow him to instigate a Fourth Great Shinobi World War and conquer the world.

In the story, Hiruko has already absorbed four Kekkei Genkai from shinobi from other hidden villages, gaining powerful nature transformations such as Steel Release, Swift Release, Dark Release, and Storm Release. He then sets his sights on obtaining a fifth and final ability: the Sharingan, which is possessed by Kakashi Hatake of Konohagakure. Hiruko had long ago placed a curse on Kakashi, known as the Puppet Curse Jutsu, which allows him to remotely control his victim. He activates this curse to draw Kakashi to his base at Mount Shumisen during a solar eclipse, which he requires to complete his plan. This sets the central conflict of the film in motion, as Naruto Uzumaki and his comrades defy orders to rescue their teacher and stop Hiruko from sparking a war.

Hiruko is depicted as ambitious, cunning, and ruthless, showing no regard for the lives he takes to fuel his power. Despite his villainous nature, his background reveals a tragic dimension; he was once a comrade of the Sannin but was consumed by his own jealousy and desire for recognition. In his final moments, after being defeated by Naruto's Wind Release: Rasenshuriken, a technique he could not absorb, he expresses a moment of clarity. He understands his mistakes and the value of bonds with comrades, dying peacefully in Kakashi's arms.

Physically, Hiruko typically appears with white hair and red eyes, wearing a large, high-collared coat bound with three belts. Through the constant modifications of the Chimera Technique, his true form beneath his clothing is said to be shrunken and grotesque, though he maintains a youthful appearance through a secret technique. As a testament to the power he has stolen, Hiruko possesses an array of formidable abilities. His Steel Release makes his body as hard as metal, granting him immense defensive capabilities. Swift Release allows him to move at speeds that are nearly imperceptible, making him difficult to strike. Dark Release enables him to absorb incoming ninjutsu and release it back at his opponents. Finally, his Storm Release allows him to summon thunderclouds to attack his enemies with powerful bolts of lightning. He is also capable of summoning a massive, multi-headed chimera beast to fight on his behalf.