Sean was the son of the original Fred Broca, a Crimson Guardsman who looked exactly like the rest of the "Fred series". Fred's true identity was unknown. Despite being only a child, Sean was aware of the fact that his father worked for Cobra. As a child, he was even present for a fight between his parents and a small team of Joes. After Fred was killed in battle against G.I. Joe, the family got a "replacement" father, Fred II. Sean and his sister Heather quickly realized that the new Fred was not their father. Some time later, Fred II was revealed to be Wade Collins, a former Vietnam prisoner of war and friend of Stalker and Snake-Eyes. Collins decided to turn his back on Cobra and his family followed him to live a somewhat normal suburban life somewhere in America, taking his true name as their own.

      Years later, just as the Joe team was being shut down, Sean asked his father's permission to enlist in the Army. Wade was hesitant due to his terrible experiences in Vietnam, but Sean failed to understand just what his father had gone through and what it meant to be a soldier. Wade suggested that Sean should write to Snake-Eyes and ask the opinion of a tough, career soldier. In his letter, Sean explained to Snake-Eyes that he wanted to join the Army because most of his school friends had no direction in life, didn't care about America and certainly had no sense of honor. He wanted to make more of himself. The letter that Snake-Eyes wrote back explained what the commando thought about life as a soldier, and told the stories of the rest of the people from the long range recon patrol unit that Wade and Snake-Eyes were a part of. Moved by the letter, Sean promised his father that he would think about all that Snake-Eyes said before making his final decision. Sean finally decided to enlist even after Snake-Eyes gave him some perspective on the Army, secretly hoping to be like the man he now considered his father.

    After distinguishing himself early in his career, Sean was invited to join a covert operations unit called the Hammer Team. After nearly a year of training the five member team performed well on their first serious mission into Afghanistan. Sean became close friends with his teammate Mikhail Derenko, a former Russian Spetsnaz commander. The team's second mission was led by the former G.I. Joe team sergeant, Duke -- who had been working for a secret government organization since the break up of the Joe team -- and undercover operative Chuckles. The goal of the mission was to take down the mercenary Firefly after an elaborate trap was set. At the same time, Snake-Eyes and his new apprentice, Ophelia planned to capture Firefly. Unfortunately, the mission was a disastrous failure. Sean watched the rest of the Hammer Team die even as Ophelia was mortally wounded by Firefly. The operation deeply scarred both Sean and Snake-Eyes.

    After seeing another person he cared about die, Snake-Eyes broke off his engagement to Scarlett. Sean took some time off from the Army and tracked Snake-Eyes down at his mountain cabin, hoping the commando could help him deal with the pain and anger over what he had seen. Snake-Eyes agreed to train Sean as a ninja, eventually with the help of the remaining members of the Arashikage clan -- Jinx, Nunchuk and T'jbang. Sean came to call Snake-Eyes "Silent Master." Almost another year passed, and Jinx discovered that Firefly was in Tokyo to meet with the "Nowhere Man", an unidentified man who was recruiting soldiers and mercenaries, including former members of Cobra. While tracking Firefly, Sean, Snake-Eyes, Jinx and Budo had the mercenary under surveillance when he met with Storm Shadow to recruit him. A confrontation followed and Snake-Eyes once again fought his sword brother, even as the others tried to capture Firefly. Duke and Chuckles arrived on the scene and soon intervened to help the ninjas evade the Nowhere Man's men. Duke then revealed that the Nowhere Man was actually Mikhail Derenko, who pretended he died with the rest of the Hammer Team. Sean was now determined to get his revenge on Firefly for killing his friends and Derenko for betraying him. At a nightclub in Japan, the mercenaries and the former Joes fought again as Derenko and his men attempted to access an old Cobra weapon locked in a vault that could only be opened by Cobra's high command or members of the Crimson Guard. Sean was shocked to discover that Derenko's latest recruit was his own father, former Guardsman Wade Collins. Wade explained that he only joined with Derenko to bring down his organization from the inside to atone for his past and to make his son proud. As Sean lunged at him, Derenko redirected his attack, causing Sean's sword to wound his father. As his father lay dying in his arms, Sean told him he had always been proud of him. Derenko made his escape, but not before Sean attacked him with throwing stars and blinded him in one eye. But it was too late to save Wade Collins. Weeks later, having passed his final trials, Sean was officially welcomed into the Arashikage clan, receiving the clan tatoo and naming himself "Kamakura" after the clan's golden age.

    Following his induction into the ninja clan, Kamakura began working for the same secret organization as Duke. In 2001, the young ninja took the surveillance photos of the Everglades Dreadnok compound that confirmed Cobra Commander's presence in the United States. That evidence lead to the reinstatement of the G.I. Joe team after seven years. Kamakura became the first new member of the Joe team, participated in their first mission, an attack on the Dreadnoks' base, and later helped defend Hawk from Storm Shadow's assassination attempt. Later, Kamakura attempted to help Snake-Eyes and Billy fight Storm Shadow and Cobra Commander, but Storm Shadow easily bested him. Kamakura was later one of the many Joes involved in an invasion of Cobra Island to battle the forces of a revived Serpentor. During that battle, he saved the life of Hawk, who had once called him a "green power ranger", wary of  having another Ninja Force as part of the team. Shortly after that battle, Kamakura joined a team of Joes on a mission to capture Cobra Commander at a hidden Red Ninja retreat in Tibet, but the Commander escaped with Storm Shadow's help. Months later, Storm Shadow had finally broken free of the Commander's mind control and headed to Japan to distance himself from his past and embrace the Arashikage traditions once again. When Junko Akita, his apprentice and lover, was kidnapped by the Red Ninjas, Snake-Eyes and Kamakura, joined Jinx and the remaining Arashikage ninjas on a rescue mission into Tibet and found that Junko had been brainwashed by the evil ninja Sei Tin. After a brutal battle with the Red Ninjas, Kamakura and the others could not stop the disturbed Junko from leaping to her death into a ravine inside the cave retreat. The surviving Red Ninjas pledged their loyalty to Snake-Eyes once again, as they had months earlier when he was declared their new leader. Days later, a ceremony was held in the mountains honoring those who had died in the battle. It was there that Snake-Eyes turn leadership of the Red Ninjas over to Billy.

    Some time later, members of the Joe team fought Cobra forces that were drawn into an attack on a train guarded by the Joes, believing that Destro was being held prisoner onboard. At the battle's end, Hawk was shot in the back by Cobra Commander and paralyzed. As Hawk recovered in a hospital bed, Kamakura stayed in the room with the general as his bodyguard. He tried to tell a despondent Hawk that he was being to hard on himself by blaming the collapse of the team on his own actions. Hawk angrily dismissed the young ninja, telling him he didn't understand what he had given up for the team over the years. In Hawk's absence, the Jugglers began to take control of the Joe team to reign it in, if not disband it altogether. Eventually, the team's roster was cut down to only a dozen Joes, while the other were reassigned to new units. The Jugglers also placed General Philip Rey in command of the team. Rey and the remaining Joes fought Cobra Commander's plans to unleash the deadly superweapon known as the Tempest. At the same time, the Joes faced a new threat in the group called the Red Shadows, who had begun targeting and murdering Joe and Cobra agents. Hawk himself nearly became their next victim before being saved by Snake-Eyes, Scarlett and Kamakura. Shortly after the threats posed by Cobra and the Red Shadows were neutralized, the G.I. Joe team was again disbanded by the military.

    One year later, the Joe team was reformed with a smaller roster of active members. Kamakura, like most former Joes, was made a reserve member of the new team. After one of the new team's earliest missions, Kamakura got word that Snake-Eyes had been killed in action. Kamakura rushed to the team's location. Angry and upset over the death of his master, Kamakura confronted Storm Shadow, who had been the only one present at Snake-Eyes' death. He questioned Storm Shadow's honesty and accused him of being responsible. After a brief fight, Kamakura calmed down and then discovered Snake-Eyes body was missing. He and the Joes eventually tracked down the body and learned that the Red Ninjas stole the body and somehow revived Snake-Eyes and brainwashed him to turn against his teammates. Snake-Eyes nearly killed Kamakura before Storm Shadow intervened and helped break Snake-Eyes free of the ninjas' mind control. Following the incident, Kamakura returned to the team's active roster.