Once there was a string of islands called Oyashima, and there was a military power called "Amamikado" which invaded other countries and expanded its domain. The Emperor of Amamikado got two sons, and the younger, he took from his mother when he was between five and ten. He killed the younger son's – Oguna's – mother, and installed a devide meant for earth golems inside the boy, sealing the boys memories at the same time. Oguna was raised as an assassin.

Already since a young age, Oguna participated in Amanikado's wars, and in several, he took out over half the enemy army all by himself. He became known as the Prince of Echoes, and was rumored to be unbeatable. When he didn't participate in wars, he did nothing but train, and sometimes, he participated in tournaments. After one of the times he took the greatest part in a war, he was praised by his father for the first and only time.

Years later, Oguna's memories was given back to him by Sugaru, a general of an enemy country, who had infiltrated Amamikado and had become Oguna's close friend. After he was forced to kill the general, he asked his father for freedom. He was not stopped inside the castle, but once he went outside the walls, he was attacked and forced to flee.

When his ”soul battery” ran out and he collapsed, he was saved by a man called Nagi. Nagi taught him how to construct spirit vessels. He stayed a while, and became somewhat of a friend with Nagi. Then Amamikado attacked, and killed Nagi, who left behind the schematics to build a much better spirit vessel than the one Oguna had, to Oguna.

A while later, he saved a group of townspeople from Amamikado, and helped them transport the food they brought along, to their citadel. He was invited by the lord Kahara of the citadel to stay for a while, and he got to know a travelling liar called Tobi. Amamikado had turned their eyes on that citadel after defeating the country Sugaru had come from, and when the situation grew tight, he helped causing a disturbance against the Amamikado army, letting the people of the citadel flee and having the Amamikado army retreat.

Not too long after, sets to killing another of Amamikago's generals, leaving before anyone has barely noticed a thing. While resting after that, and after having paid maintenance to his doreki, he overhears some people talking about an enemy who has been captured, and is set to be executed. The name mentioned is Kahara. Oguna left for the stronghold where Kahara was captured, and confronted Imasuhito, one of the four higher generals, and another general, Oohiko. While Oguna fought Oohiko, Imasuhito stabbed his sword through Kahara's chest, and Oguna went berserk, almost killing everyone on the locarion, until Oohiko stopped him, saying that Kahara was still alive. He told Oguna to leave, and that he would save Kahara. So Oguna left, trusting the man to keep his word.

When he reached another town, he overheard the guards talking about a murderer on the loose. Since he was new, the one manager of the town confronted Oguna, but recognized him almost immediately. When Oguna didn't know who he was, the man told him that they had fought in tournaments as children, and that Oguna beat him all the time. Then he tol Oguna that they were more even now, because he had a doreki as well. Having one isn't the best thing though, because it can consume a person's feelings, and make a person lose his mind, like Oguna did when he thought Kahara died. So Oguna wasn't very happy about Tagino's choice to have a doreki embedded in his skin. Either way, Oguna was invited to stay at Tagino's place, and so he did. During the night, however, Oguna was attacked by the murderer roaming the town, and to his shock, realized that it was Tagino, under possession of the doreki. When Tagino didn't return to his senses, Oguna was forced to stab him, in an attempt to snap him out of it. For a brief moment, Tagino did, but then the doreki took over again, right before he died, and after that, Oguna decided to keep struggling alone, without relying on anyone else.

When he was in an alley in the port of Tokai, about to end the crows pain, he is stopped by Izumo, who showed him that the crow only had gotten a wedge bug in its throat. Oguna left after that, and went to stake out a General Fudaru's manison. In the evening, he attacks the manison and ultimately ends up helping Izumo and Kumaso by killing Fudaru and several of his guards. He is hired by Izumo to join their journey.

They head toward Jagara, the only warriors that can resist Amamikado, a warrior tribe of amazons. When they reach Jagara's first line of defense, Yomogahara, they come across a battle field, a fight between Amamikado and Jagara. While watching the battle, they are attacked by earth golems. He bring along an earth golem's core. As they pass through the Forest of Confusion, the Jagara's last line of defense, they come across yet another battle, between Jagara and a group of Amamikado's assassins. Oguna interferes and after all three of the Takeru's joined the battle, the last assassins flees. Izumo offer their help to Jagara, and they are brought along to the Jagara fortress. They get an audience with the three queens, and are tested. Oguna intended to go through thte first trial, but Kumaso beat him to it – to the trial of Wisdom. Oguna instead goes through the second trial, which is the Trial of Might.Both clears their trials perfectly, and Izumo clears his through luck and a little cheat. They are all three faced with a visionof a woman telling them to leave.

When the people of Jagara have a feast, Amamikado attack, and Izumo finds out about Oguna's identity. The eldest queen of Jagara are captured by Amamikado, and Oguna and Izumo save her from being killed. The evil sword Kusanagi are awakened and possess Kumaso, who kill queen Yamato. Oguna, Izumo, advicor Hatahatabiko and queen Miyazu are forced to flee.

Getting through a forst of illusions, they find the sacred place where the sword of Susanoh is sealed. Oguna fight a losing battle against the guardian of the Susanoh, and is saved by Izumo, who gains the sword.

They then head to Amamikado's capital, and face off agaisnt the Emperor, and to get Kumaso back to normal. Oguna face his father, as Izumo battles Kumaso. In the battle agaisnt the emperor, Oguna's soul container is destroyed and he dies, but pulls through thanks to queen Miyazu. Together, Oguna, Izumo and Kumaso face and defeat theemperor, with Oguna giving the finishing blow.

Kumaso sets off to a trip with Yamato to repair all the damages he caused with the sword of Kusanagi, Izumo goes to look for new treasures, and Oguna became a guardian of Jagara.