Shima Sami was born in battle. During the Clan Wars, his mother gave birth to him on the battlefield. Though weak from the rigours of childbirth, she was still an exceptionally strong woman, with a powerful desire to see her child to safety. She managed to fight her way free of the battlefield, and find the house of an old fisherman and his wife. There she entrusted her infant to their care, and then died from a combination of the injuries suffered while fighting, and from simple exhaustion.
Sami was named after his mother, and was raised during hard times, when war raged throughout the various countries. Yet somehow, that one house with the old fishing couple went untouched by violence. This did nothing to prevent Sami from learning how to fight. Though as he grew he assisted in the various duties of fishing, he spent his free time either learning how to play the guitar, or fighting. He trained his fighting skills in seclusion, and so when some mercenary soldiers arrived and made demands of payment on Sami's adopted parents, they were unprepared for the quiet, unassuming boy to kill two of their number in as many seconds.
He was not a ninja, or a match for trained soldiers, and so was beaten for his insolence. The leader of the patrol, however, was impressed with Sami's skill, and murderous instincts, and chose to "recruit" him to join a local warlord's ninja forces. Sami was reluctant to leave his parents behind, so the leader killed them so that Sami would have nothing holding him back. Sami's hate for the soldier leader knew no limits from that point on. Still, he went with the soldiers willingly, and without any further violence on his part. Along the way to camp, the soldier captain, named Mishima Kento, explained to Sami why he had done what he did. Mishima saw everyone as expendable. Life was to be taken or given at the drop of a hat, to fit the needs of a given situation. Sami had killed two soldiers because it was necessary to protect the old couple who had adopted him. Mishima had slain that same couple because it was necessary to provide motivation to come with the soldiers and receive training. He did not care if Sami hated him, only that he become strong and serve the will of the warlord named Kaguya Moto.
Sami trained with other children who had been forcibly recruited, and trained as few had ever trained before. He threw everything he had into learning the ways of the shinobi… But few ever saw him do so. He still preferred to train in seclusion, and to present the public face of being more interested in his guitar-playing. This misdirection brought him a great deal of grief from bullies, and his half-hearted attempts to defend himself only made him seem like an easy target for further harassment. And yet, when it came time to prove his worth against live targets, his opponent was dead in under ten seconds. It had taken only three years of training for Sami to reach the level of a Genin, at the age of 11.
Soon after, as war continued to rage on and beyond the shores of the Land of Water, all able-bodied ninja in the warlord's service were recruited to defend their master. Sami was not Chuunin-level despite his intense training, and he suffered many brushes with death, despite the foes he slew in exchange. However, the constant struggle gradually strengthened Sami, forcing him to learn and improve his skills, or else die. Sami had no intention of dying. Eventually, he made a name for himself on an assassination mission in which his team leader was captured, and he had to strategically use the capabilities of his companions to get close enough to kill the leader of an enemy force. Not only did he succeed in this, but he also killed those interrogating his team leader, so that no information about the warlord or his troops would escape. Unfortunately, his team leader was too injured by the interrogation to travel quickly.
Sami killed him. It was just as Mishima said: lives were to be ended or surrendered whenever necessary. That was a lesson that Sami had taken to heart. This act of cold-hearted murder would have gotten Sami in trouble, but Mishima managed to conceal Sami's actions when he was reported to by the youth himself. Mishima then had Sami re-assigned to his own forces, so that he could keep an eye on the younger shinobi, and teach him to be a powerful instrument of wrath. Under Mishima's tutoring, Sami grew far stronger than he had been before. He was Chuunin-level at 13, and a Jounin-level ninja at 15.
Then came the day of the great offensive of the warlord's ninja — as he attempted to counter the attempts by another country to invade the Land of Water. Sami had worked under and with Mishima despite his hatred of the man, because he knew that he needed to become stronger. He had allowed some of his training to be observed, but made sure what progress he showed was below his actual capabilities. In this way, he kept Mishima Kento thinking that he was weaker than he really was. When a squad of ninja, including Mishima and Sami, were sent to destroy the ships of the invaders, preventing them from fleeing easily back to their own country or dropping off any more troops, Sami followed orders as he always had. He planted explosive tags on the boats, and then set them off when at a safe distance, decimating the enemy fleet.
But Mishima didn't come back with Sami. This was because Kento had tried to sneak on board one of the ships, to capture the leader of the fleet for ransom purposes. The naval leader was one of the greatest the enemy had ever had in their possession, and they would surely pay a great deal for his return. Mishima's greed resulted in his being on one of the ships when Sami blew it up. He knew Mishima was there. He could have waited. But the mission came first. Besides, he didn't see any reason why the man he hated should get rich on his master's time.
With no leader anymore, and no loyalty to the warlord Kaguya Moto, Sami and his team reported directly to the Daimyou. The single-handed destruction of the enemy's fleet by Sami earned him a special position with the Daimyou when the war ended. As Kirigakure was formed, and began to be stabilized, Sami and six others were chosen as the "Seven Swordsmen of the Mist" and assigned to act as advisors and WATCHERS for the Mizukage, to ensure that he was not allowed to act unchecked. Sami quickly made use of this position of power to put forth suggestions to the Mizukage that the harassment and/or killing of civilians without just cause be outlawed.
Previously, it was assumed that civilian rights were superceded by the rights of the military, and any actions taken against "uppity commoners" was perfectly legal, regardless of what that may entail. Sami saw this as being inefficient, unproductive, and harmful to the Land of Water as a whole. Without the workers, there was no food, no construction, or countless other things. With no merchants there was no trade, and no wealth to fund the shinobi armies. And a population oppressed eventually rises up to overthrow those doing the oppressing.
This practicality has since served Sami well, as he functions both as a grudgingly accepted advisor to the Mizukage (and a spy for the Daimyou), and a leading figure in peace talks with the other Great Nations — while at the same time helping to train Kirigakure's shinobi to be ready for war. To Sami, there's no point in growing weak during peace time, because peace can be shattered in an instant. By always being ready for the potential of conflict, peace can be maintained more easily. After all, he was preparing for combat even when he lived in peace with his adopted parents. Yet he was not strong enough to defend them when the time came. He plans to never be too weak to defend what is important to him, ever again.
