|Affiliation||Gotei 13, Soul Society|
|Position||Captain of the 4th Division|
|Previous Position||Captain of the 11th Division|
|Previous Division||11th Division|
|Previous Partner||Seinosuke Yamada|
|Base of Operations||4th Division HQ|
Retsu Unohana, formerly known as Yachiru Unohana, is the captain of the 4th Division in the Gotei 13. She is one of the oldest and most experienced captains, and is the Soul Society's best healer. Her lieutenant is Isane Kotetsu.
Unohana has the appearance of a slender and very youthful and beautiful woman with blue eyes and black hair. She wears the standard Shinigami captain uniform apart from using an obi instead of the normal sash. Her hair is long and is always worn as a large braid in front.
Unlike most Shinigami who carry their Zanpakuto in their sash, Unohana has a large string attached to the sheath of her Zanpakutō and carries it over her shoulder, or has her lieutenant, Isane Kotetsu, carry it for her, whenever they are together on the battlefield.
Unohana has a gentle and warm personality that augments her appearance. She is a soft-spoken, polite, and caring woman who uses honorifics when addressing everyone, including her subordinates and the enemy. She rarely shows any signs of panic or distress, and has a great sense of duty. Despite her sense of duty, she will also heal almost anybody around her. With her grace and kind manners, she lets others know quietly that while she may be soft, she is not to be taken lightly. Despite her gentle nature, several members of the 11th Division and even her fellow Captains fear her.
The reason for this fear is that Unohana was the first captain of the 11th Division. During that time, she was a malevolent, sadistic villain who took great delight in inflicting slow and painful deaths on unworthy adversaries. It is even implied that the primary reason she learned healing Kido was so she could test her attacks on her victims and see how much damage they could take before a single blow would finally kill them.
Centuries (or perhaps millennia) ago, Yachiru Unohana was known as the Soul Society's most diabolical criminal and a founding member of the Gotei 13 after being sought out by Genryusai Shigekuni Yamamoto. She created the 11th Division and became its first captain, thereby creating the title 'Kenpachi.' At some point, she learned medical Kido as a way to prolong a fight.
After a time, Unohana was tasked with eliminating warriors in the outer Rukongai. During one of these excursions, a bored Unohana encountered a young Kenpachi Zaraki, who was a nameless child at the time. The boy attacked her on sight and managed to wound her, which excited Unohana into fighting him. She easily defeated the boy, but spared his life, believing that he would be a stronger Kenpachi than her one day.
At some point after this, Unohana became the captain of the 4th Division and changed her first name to Retsu. She also gave up fighting for the most part, though she remains highly feared by her peers and subordinates. When Sosuke Aizen faked his death and enacted a complicated plan to betray the Soul Society, Unohana studied the false corpse and managed to figure out that it was an illusion, though she was unable to prevent his escape.