The story begins in a place called Ionia, which is made up of many islands in the northeast of the Rune Land, where people seek peace in all things.
Yaso was a genius apprentice at one of Ionia's well-known kendo dojos, and was the only student of his generation who could master the legendary Mikaze swordplay. Yaso is an indomitable man or an agile swordsman who can use the power of the wind to slay enemies. The once triumphant warrior was discredited by false accusations and forced into a desperate battle for survival. Even if the whole world is already his enemy, he will do everything in his power to bring sin to justice and restore himself
Most people believed he was destined to be a great hero. However, because of the invasion of Noxus, his fate was changed forever. Yasso was in charge of protecting an Ionianese elder at the time, but he thought that his sword would change the tide of battle, so he left his post and threw himself into the battlefield. When he returned to the elder, he found that the elder had been killed.
The discredited Yasso willingly surrendered himself, ready to spend his life compensating for his dereliction of duty. But he was shocked not only by charges of dereliction of duty, but also of murder. Although the guilt left him confused and miserable, he knew that if he did not act, the real assassin would go unpunished. Yaso drew his sword and escaped from the dojo, and he knew very well that he had committed another crime of treason, and the whole of Ionia would be his enemy. For the first time, he fell into true solitude and embarked on a life journey to find the true murderer of the Elders. Yaso spent the next few years wandering around, searching for clues that would lead him to the real culprit. Throughout, he was ruthlessly hunted down by his former classmates, constantly forced to fight or die. His mission drives him forward until he is chased by his most formidable rival, his brother Yong'en. Bound by traditional etiquette, the two swordsmen first bowed to each other and then drew their swords to fight. In the moonlight, they silently swung their swords round and round. When they finally charged forward, Yong'en was defeated by Yaso; the sword flashed, and Yong'en fell. Yaso abandoned his sword and rushed to the side of Yong'en.
Bound by traditional etiquette, the two swordsmen first bowed to each other and then drew their swords to fight. In the moonlight, they silently swung their swords round and round. When they finally charged forward, Yong'en was defeated by Yaso; the sword flashed, and Yong'en fell. Yaso abandoned his sword and rushed to the side of Yong'en. Mixed feelings, he asked his brother how his relatives thought he was guilty. Yong Eun said, "The elder died in the Wind Sword Technique. Who else can do it? Yaso instantly understood why he was being charged. He again claimed his innocence and begged his brother to forgive himself. As his brother slept forever in the crook of his arm, his tears slid down his cheeks.
Under the rising sun, Yaso buried Yong'en, but he had no time to mourn. Soon someone else would come after him. The brother's revelation had given him a whole new purpose; he now had clues that would lead him to the real culprit. While swearing, he packed his bags, reluctantly bid farewell to the tomb of Yong'en, and embarked on a journey accompanied by the wind.