Retsu Unohana

Retsu Unohana (卯ノ花 烈, Unohana Retsu) is the captain of the Fourth 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 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. Over 100 years ago, she did not have the large braid, instead styling in front of her as a loose ponytail.

Unlike most Shinigami who carries their Zanpakutō 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. Unohana 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, shown in the times that she orders Hanatarō Yamada’s imprisonment and Isane Kotetsu’s chasing of Renji Abarai when he runs away with Rukia Kuchiki. Despite her sense of duty, she will also heal almost anybody around her, including Renji after he was defeated by his captain, Gantenbainne Mosqueda when she arrived in Hueco Mundo, and the Visored, referring to them as allies despite Shinji's reluctance to do so. 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 Eleventh Division and even her fellow Captains fear her.
Unohana likes strong flavored food, preferring it to bland tasting dishes. In her free time, she climbs mountains throughout Rukongai, during these excursions, she collects medicinal herbs. Once a month, she holds an ikebana class for the members of her division. Unohana is also the President of the Ikebana Club (Flower Arranging Society.)

 Info from :  http://bleach.wikia.com/