Ashido Kanō (Seireitou)

Ashido Kanō (狩能 雅忘人, Kanou Ashido) is a male that once served a seated officer within the. After becoming trapped in during a failed operation, in which all of his squad members were killed, Ashido chose to remain there and continued slaying  for centuries in the hopes that he could protect the  and  in his own way.

Quotes

 * (To ) "In order to protect Human souls, and keep the promise I made with those who lost their lives, I've stayed here and fought."
 * (To Rukia) "I just wanted my friends to hear you speak. It's been a while since they heard a Shinigami's voice."

Behind the Scenes
He was originally set to appear in the Bleach manga during the arc, but had to be cut by series creator  due to time issues.