Unlike many contestants of the Thunderdome, Kozuri participates in the arena under paid contract. While the other participants compete to fulfill personal vendettas or prove their worth, Kozuri competes to complete a contract to win the tournament and bring the grand prize to his employers.

Kozuri was raised in an assassin village and was trained from birth to be a silent killer. He was an only child, being the only one of five sibilings to survive the "birth trials" which included being thrown into a pool of water and having to swim to safety at birth. As per tradition, he was raised along with the rest of the village boys by the elders while his parents were on their own contracts. Every day was an endless grind of exercises and training and by the age of fifteen, Kozuri was qualified to participate in contracts with an accomplished partner. On his very first contracted mission his partner was killed early on and Kozuri barely managed to complete the mission single-handedly, taking down a local slave trader. However inexperienced Kozuri was, he had impressed his village elders with his ability and potential. It wasn't long before he was given his second contract, this time to eliminate a brutal and reputable warlord. It was the assassination of Lord Saito that reserved a place in legend for Kozuri who, at only age sixteen, was given the right to leave the village and make his own fortune elsewhere.

Kozuri roamed throughout the land, making a living off settling vendettas for drunkards at bars and collecting debt for various brothels. By the age of twenty four Kozuri had not pursued a major contract since his takedown of Lord Saito. Feeling pressured to live up to his reputation, Kozuri had become content with the more quiet life of roaming from village to village in search of work. It was one day while roaming in the forests that Kozuri had an epiphany. Of all the people he had killed, it was only Lord Saito's story that continued to be retold to this day. What made Saito different from all the other people? It was because he was famous and powerful. Kozuri knew that some day he would perish like all those that had fallen by his hand and he wanted to be remembered. Whether it was by word of mouth or by written record, it didn't matter. As long as his tale was remembered, it would be enough.

An assassin once again, Kozuri sought out major contracts; taking down warlords and officials was the usual work. And once again, the tales of Kozuri's accomplishments spread across the land like the plague. Kozuri's high success rate was attributed to his rare supernatural affinity with water. He was able to manipulate the element to his will and many of his targets had been eliminated at full moon. In the stories told by candle light and drinks, Kozuri was a vengeful spirit who sought to repay an old grudge and killing all in his wake. The truth however, was far from that. Kozuri remained neutral towards his job and was loyal to his contracters. Anything he did had to be specified in the agreement. Most of Kozuri's money actually went to people in need who he would find in his spare time. He didn't care about wealth; he only kept as much money as he needed to buy supplies and his next meal.

Eventually in the years that passed, Kozuri decided it was time to settle down and perhaps even start his own village. Stories of his deeds had become legend and were now commonly told throughout the lands. He had personally ended three various family reigns and established several dynasties through his contracts among other things. The village, Kozuri told himself, was a sign of rest and not resting on laurels. However, in the thirty seventh year of his life, a new challenge approached; The Thunderdome.

Emerging as the victor of the Thunderdome promised certain fame and fortune. The prize money was of behemoth proportions and enticed many contestants. Kozuri was initially hesitant on competing, but soon changed his mind as he accepted a contract by the Emperor himself to win the tournament and bring he money home. Kozuri didn't mind, he only needed his story to be remembered.