I guess if I had to give my character a little bio it would be this:
So 1,400 years ago, there was a special division or squad called "Squad Zero". It was a squad that consisted of the two of the strongest shinigami besides the captain commander. In this time period, the three most powerful shinigami in squad zero were Kurosaki Isshin and Nobutada, and the now captain Yamamoto. Nobutada stood out from his brother because of his long, orange hair and black samurai armor. The three were sent on the most dangerous missions and were rarely seen in the soul society, making the squad of two seem like a myth more than reality. They would report directly to the captain commander and if necessary to the rest of the 13 court guard squads.
One mission, when Isshin was 23, Nobutada and Yamamoto were both 33, they were attacked by an unknown enemy. the three held their ground but seemed to be no match. Isshin was badly injured and once the enemy was about to deliver the final blow to him, Nobutada stepped in the and took the hit for his younger brother, while finishing his opponent off with his bankai. Everything seemed fine when Nobutada's reiatsu began rise dramatically, startling Isshin and Yamamoto. A white substance began protruding from his face and took the form of a dragon. Red eyes shown through the mask and was met with a fierce roar that shook the land. The first vizard had been born. Nobutada began attacking his teammates, not knowing friend or foe, when Yamamoto struck him down with his then incomplete sokotsu, which didn't kill Nobutada.
Nobutada was then taken back to the soul society and through many tests,was reawakened in a dark room that completely sealed off his reiatsu. A note was left beside him written by his brother. The not stated that the then captain commander deemed Nobutada a dangerous being and threat to the 13 court guard squads, and had him sealed using a dark kido technique called "Kurai kodoku no kage no ryōiki" or "shadow realm of dark solitude". the only way he would be freed is if a captain commander released the seal. Nobutada was also in formed that Squad Zero was disbanded and Yamamoto was being promoted to captain commander soon. These words enraged Nobutada, which forced his hollow-side to take over for a bit. With his new found powers, Nobutada lied in a realm that perpetuated him to train and get stronger, hoping to regain his honor: for a samurai can not stand the shame of a defeat...