Hyakuoku Getsueikirite

was an ancient and the founder of the Getsueikirite Clan. He is remembered in history as the first user of Shukai, and the one who originally defeated Lucifer.

Appearance
Hyakuoku was a man of average stature, standing at equal height to Genryūsai Shigekuni Yamamoto. Though youthful in appearance, according to Yamamoto, he was quite old when Yamamoto was a young man himself, hinting at just how ancient he truly was. He possessed long white hair, red eyes, and red markings on his face. Like most Shinigami, he wore a shihakushō, though his was more form-fitting than the more modern version. Over this standard shihakushō, he wore a blue-hued battle armor, which covered most of his torso, his flank, hips, and shoulders.

Personality
From what little is known of him, Hyakuoku, being born in an age of strife and war, was a very dutiful and purposeful man. He was renowned for being very compassionate, and staunchly opposed Yamamoto's more genocidal way of going about things, even though both he and Yamamoto fought for the same purpose; to bring balance to the worlds, both of spirits and living beings. Though he detested fighting, he saw it as a necessity, given the evil that was rampant in his time, as well as the never-changing, stubborn, Genryūsai Yamamoto.

Ultimately, Hyakuoku was a revolutionary, and a teacher, who found great fulfillment in spreading his thoughts and ideas to the Shinigami of the age, earning him a massive following, which eventually became the Getsueikirite Clan. It also earned him powerful enemies, such as Yamamoto's band of Shinigami, as well as Lucifer, an incredibly evil Sōzōshin during his day and age. He was also seen as an unmovable figure, such as when he stood down Yamamoto while the two disagreed on how best to deal with Lucifer's insurrection of Soul Society.

Hyakuoku was also a man of action, refusing to stop what he was doing once he held firmly to a belief or ideal. After the formation of his group of Shinigami, which eventually became the clan he founded, he became very protective of them, often only fighting in his latter days, in defense of them.

History
Hyakuoku was born as the middle child of three brothers, in an era where Hollows freely hunted both Humans and souls without opposition. By the age of nine, both his younger and his older brother had been killed by Hollows, forcing him to harden his heart, and grow up faster than most. Along with his father, and a growing number of souls bound to stop the Hollow menace, he formed the "Balancers" — a group of souls determined to fight off Hollows and balance the universe's souls. One of these Balancers, Ōetsu Nimaiya soon armed the growing number of souls with a new weapon; the Zanpakutō, which allowed them to channel their souls into weapons and then purify the Hollows as they killed them. As a soul with significant power, even at a young age, Hyakuoku was given an, which allowed him to fight against the Hollows with ease. As the young Hyakuoku matured, he began to realize that Hollows weren't the only endangerment to the balance of the universe's souls, but also the actions of the Soul Society's leadership. During this time, the Balancers, which had been previously united, divided into two groups. Those who supported Shigekuni Yamamoto, the founder of the Genryū School, who believed that the Balancers should stay out of the affairs of the leadership, and the followers of Hyakuoku, who believed that the evil in the leadership, such as Lucifer, needed to be dealt with.

Eventually, the offending sides began to fight among each other, and Hyakuoku's band of Balancers began to be known as mercenaries, and were called, a name originally meant as a derogatory term. During this era of strife, Hyakuoku named himself, after single-handedly bifurcating a Vasto Lorde-level Menos with a moon-shaped Hollow mask. Both sides continued to war, carving a path of carnage through the wilderness of Soul Society. Hyakuoku's group eventually settled down, creating a village, which would later expand to become the Rukongai, to base themselves from; eventually taking on his nickname as the group's overall name. Deeply grieved from the losses being produced by the war, Hyakuoku called a parley between the two forces as what would become the, and attempted to reason with Genryūsai, by getting both groups to agree to defeat Lucifer, thus uniting them under a singular cause once more. Nevertheless, Yamamoto refused, causing the two to battle once more; finally resulting in a direct loss for Yamamoto. Sometime following this, he obtained Shukai and sealed Lucifer away, becoming a legend forever in Soul Society's history. He was also known to have fought the earliest incarnation of the Yonkō, due to the destruction they wrought on the Soul Society — defeating and killing his longtime enemy, Guren Kurosaki.

Zanpakutō

 * As an Asauchi, Kōdai Kōzui appeared as a regular with a white hilt. After becoming his Zanpakutō, Kōdai Kōzui doesn't change much, except for gaining two crescent marks at the base of the blade, on the guard, as well as becoming darker on the hilt.
 * Shikai: It is released by the command.
 * Bankai: Not Yet Revealed.
 * Shukai: Not Yet Revealed.

Trivia

 * It has not yet been explained how Hyakuoku is the first user of Shukai when Nimaiya invented it.

Quotes

 * (To Genryūsai Shigekuni Yamamoto) "I will not sit here motionless while Soul Society hangs in the balance, Genryūsai. If you will not stand with us, then stand aside and let us by!"