Shukaku had been an outcast for his entire life. Though he was created at the same time as his eight siblings, he never quite fit the demonic mold. To Kurama, he was an inferior being whose existence barely deserved acknowledgment. To the other seven, he was a shameful excuse for a demon thanks to his outgoing and boisterous nature. Though the Sage of the Six Paths viewed all nine of the tailed beasts as equals, he failed to prevent Shukaku's mistreatment even while he was alive. After living through decades of mistreatment and verbal assaults while the sage lived, Shukaku eventually secluded himself from his brethren deep within the desert where he could change the entire landscape on a whim.

After wandering aimlessly through his new haven, Shukaku eventually stumbled upon a lone village within the desert. He saw them scurry about from place to place like tiny mice during the cooler hours of the day only to flee at the slightest hint of an oncoming sandstorm. Taking pleasure in the excitable nature of the humans, it didn't take long for Shukaku to stir up more than just mere storms. Every once in a while, when the moon hung full in the night sky like the shiniest of pearls, Shukaku would terrorize the humans. As weak as they were back then, they could only scream in terror as the massive demon toppled buildings with his tail and taunted his prey by raking his claws down the streets until only gaping crevices remained. Shukaku basked both in the light of the moon and in the glory of his supremacy. It was only once the panic nearly reached its peak that Shukaku truly thrived. When the horrified screams of the citizens echoed in his ears to create a symphony of unbridled terror, Shukaku would scoop up dozens of the inferior creatures with his gaping maw before shattering all of their bones with his powerful jaws. After gorging on the flesh and blood of his victims, Shukaku would retreat and wait for the bloody cycle to begin again.

After decades of asserting superiority over the humans, Shukaku eventually met his match. The second Kazekage, a skilled wind user and chakra manipulator, eventually subdued him. After distracting the beasts with fierce gusts of wind, he chained the mighty demon with chakra chains before sealing him into his first host- a young boy. The first tailed beast to be sealed, Shukaku could easily manipulate his host through the barely functioning seal. A few nightmares here, a few surreal hallucinations there, and the boy was broken. The villagers sped up the decay of the hosts mind by avoiding any contact with him much as the other demons had done to Shukaku, but this did not make the two bond in the least. It only shattered the host's fragile will and left Shukaku to mold it as he saw fit.

First it was the empty eyes then it was the twisted smirk. Before the villagers realized it, the host had started having his personality distorted by Shukaku. Harsh whispers to spread his agony to the rest of the world spurred him on. From children to seniors, no one was safe. The streets became littered with corpses. The living were too fearful to go outside and bury them properly so that the few who ventured outside by necessity often saw mutilated and maggot ridded bodies before they too became casualties. After being pressured by the council to save the village from the monstrous young man who tore out throats with his teeth and drank blood, the Kazekage subdued Shukaku once more only for him to be sealed in a newborn girl months later.

Believing the seal to be incredibly stable, the council allowed the girl to fade into the background. Shukaku bided his time until human flaws gave him a suitable opening in the seal to shove himself through. This time, the host's father was to blame. An alcoholic war veteran, he often came home late only to enter heated arguments with his frail, aging wife. One day the arguments reached a whole new level of ferocity. The young host came home one night to witness her father, staggering and swearing, standing over the crumpled form of her mother. The woman was still breathing, but dark bruises and blood stained clothing covering deep gashes were enough to set the host on edge. Screaming in horror, she pleaded for help. And it came.

The man was slammed into the wall within seconds. He hollered obscenities at his unconscious wife and his newly possessed daughter, but he was helpless. Within the brief moments during which he managed to take advantage of his host's weakness, Shukaku rammed gallons of sand down the man's throat until he choked to death. The girl's mother never woke up from her earlier beating and died before help could arrive. After that incident, Shukaku's second host was never the same. She lived the rest of her days overwhelmed with guilt over the death of her parents. She secluded herself in a cave for the rest of her days. Her emotional instability caused the seal to degenerate until Shukaku freed himself completely. Te seal trapped copious quantities of his chakra into the girl's body though. Seeing this as one last chance at acceptance, Shukaku tried one last time to fit in.

He compressed his form down to the size of his remaining chakra reserves and used a mirage based genjutsu to appear human. Taking the form of a rather large and jolly priest, Shukaku made himself comfortable within the local temple. He was pleasantly surprised by human generosity at first. The young helped the old and sick worship as they pleased as they all prayed together for a better future. Shukaku even developed a fondness for the wine of the church since it loosened the chained binding everyone's minds a little; it freed mouths and bodies to act on the heart's will rather than the mind's. But Shukaku eventually saw the darkness that chases humans ceaselessly. Beggars died cold and alone in the streets. Battles happened as often as sunrises though they varied in magnitude day by day. Seeing this strife, Shukaku lost hope for himself and the seemingly irredeemable humans. He returned to his rampaging once more though he now carried the sins and burdens of all creatures in his heart.

When the fourth Kazekage eventually captured Shukaku and sealed him into his unborn third child, Shukaku felt a hint of remorse. The woman who would die upon birthing his host had a certain light in her soul. Glowing gently, it warmed the lives around her. Even the Kazekage was deeply moved by her presence. She had enough love in her for everyone, even the child who would inadvertently kill her and for the boy's father who had left the village long ago. When the women finally died, Shukaku shed a single tear. Perhaps there had been one human who could have accepted him, but now she had died if only in the physical sense. Her spirit fused with his sand to create an eternal shield for Shukaku's newest host, Gaara.

Out of respect for the boy's mother, he left Gaara alone for much of his early life. The imperfect seal made insomnia unavoidable however and the child lacked sufficient chakra control to manipulate the sand well. After Gaara's chance at a somewhat normal life blew up in his face, Shukaku took it upon himself to mentor him as if Gaara was his own kit. They even grew to understand each others deepest wants and needs. It was never meant to last though. Kurama's host made sure of that. Shukaku's cheerful façade appeared for the last time on that fateful day. After losing hope in his ability to help someone else through the pain of being ostracized, he lost faith in himself fully once a clay user and the boy's father appeared and wound up tearing him from the closest thing he had to a friend since the Sage of the Six Paths. It wasn't until he heard tale of his last host, Kurama's host, and the new alliance that he could believe in a brighter future again.