Retsu Unohana , formerly known as Yachiru Unohana, was the former captain of the Fourth Division in the Gotei 13. She was one of the oldest and most experienced captains, and was Soul Society’s best healer, as well as the first person to wield the name “Kenpachi”.Her lieutenant was Isane Kotetsu. She also formerly served as the Captain of the 11th Division. After she was cast into Hell, Unohana gained the epithet of “Death Sword” .

Unohana has the appearance of a slender and very youthful woman with blue eyes and black hair. She wears the standard Shinigami captain uniform apart from using an obi instead of the normal sash, which hides her well-endowed bosom. Her hair is long and is always worn as a large braid down the front of her body. Over 100 years ago, she did not have the large braid, instead styling in front of her as a loose ponytail. While maintaining a kind and gentle look at most times, during her battle with Kenpachi Zaraki, her eyes appear gloomy and very menacing. She also wears her hair down for the first time and is revealed to have been covering a notable scar in-between her collarbone, inflicted by Kenpachi when the latter was young. Before Kenpachi inflicted that scar on her, she did not tie her hair in front of her, instead wearing it down at all times.