Mitsurugi was born in Japan to a peasant family during a time of war. Nevertheless, this did not stop him from becoming a renowned mercenary. His reputation earned him nicknames such as "The Mercenary of War," "One Man Army," and "Demon."

As a mercenary, Mitsurugi fought in and triumphed over countless battles. Every enemy who faced him in combat feared his invincible blade. That was until a new breed of weapon was introduced. Rifles known as Tanegashima were brought in for practical use by the famous shogun Nobunaga Oda.

For Mitsurugi, who relied purely on his strength and skill, the Tanegashima was a serious threat. Simply by holding this "pipe," even the lowliest foot soldier could become a powerful force on the battlefield. Unable to accept such a preposterous notion, Mitsurugi looked for ways to defeat the rifle. Unfortunately, he could not find a good way to overcome the new weapon. Frustrated, Mitsurugi challenged Tanegashima to a duel, but lost when he was shot through the right shoulder.

But this did not deter Mitsurugi's spirit. He resolved to defeat the rifle by finding a powerful weapon that would enable him to achieve this goal. It was then that he heard a rumor from overseas about Soul Edge. At the time, a man known as Nightmare wielded the giant, grotesquely shaped blade. Hearing stories of its immense powers, Mitsurugi set off across the ocean in pursuit of the sword without a moment's hesitation.

He headed west towards Europe, where Nightmare supposedly roamed. Travels through foreign countries were difficult for Mitsurugi, who was unable to understand the languages of the places he visited. Nonetheless, he continued his travel, making ends meet by fighting battles as a mercenary. The added benefit of his mercenary lifestyle was that he was able to maintain his fighting form.

But time was callous and unforgiving. Eventually, rumors that Nightmare had disappeared reached Mitsurugi, and Soul Edge's trail ran cold. Mitsurugi was still unwilling to give up, and continued his search around the world's battlefields for signs of the ultimate blade.

Four years after his quest had begun, while visiting a castle near the Ming frontier, Mitsurugi stumbled upon the trail of Soul Edge. It was a metal fragment of Soul Edge that he came across by accident.

Walking past one of the back alleys of the city, Mitsurugi came to a halt when he witnessed several assassins surrounding a gravely wounded man. When the assassins saw Mitsurugi, they pounced upon him, intending to leave no eyewitnesses behind. A vicious melee ensued, and Mitsurugi drove back the assailants, saving the man's life as a result.

The badly injured man handed Mitsurugi a piece of metal-perhaps he thought that he would be unable to accomplish his mission with his wounds. He asked Mitsurugi to keep it safe. He seemed afraid to let it fall into someone else's hands, but he would not explain any further. Without another word, the man vanished into a dark alley.

Looking at the metal fragment in his hand, Mitsurugi pondered, "If Soul Edge was so powerful, why would it shatter?"

Mitsurugi had a difficult time believing the man who gave him the fragment, but there was no denying the sincerity in the man's eyes. "Besides," Mitsurugi reasoned, "why would a man on the verge of death lie to a complete stranger?"

Soon after, a grave story circulated through the castle. Apparently, a servant of the Ming Emperor arrived at the castle, demanding the "Sword of Heroes." When the servant steadfastly refused to leave without the sword, the lord of the castle slew him, exclaiming that he could not turn over something he did not have. "War is coming," thought Mitsurugi.

He sensed the same storm brewing that he had felt before in countless battlefields.