Retsu Unohana

is the Captain of the Fourth Division in the Gotei 13. She is one of the oldest and most experienced captains, and is noted to be a very skilled healer.

History
Although not much is revealed about her past, it is said that she has been a captain for over 200 years; along with fellow captains Ukitake and Kyoraku. This makes her one of the oldest captains among the Gotei 13, despite her rather youthful appearance. It is vaguely hinted that she may be the second eldest captain, as both Ukitake and Kyouraku have hinted this on one occasion.

Soul Society Arc
Retsu Unohana first appears during the captain's emergency meeting called by Shigekuni Yamamoto-Genryūsai. However she says nothing at this time, and remains silent throughout the constant bickering between her fellow officers. She is next seen after Sōsuke Aizen's apparent death, in which she confirms to Sajin Komamura and Kaname Tosen that he is truly dead, and appears shortly afterwards when Hanatarō Yamada is "caught" by Jūshirō Ukitake and brought before Unohana for judgment. Despite the reasons put forth by Ukitake, she determines that Hanatarō must be imprisoned on account of the fact that he is a seated officer in her division and may have incidentally aided in the harm that the Ryoka had supposedly done within the Seretei.

As head of the medical relief division, Retsu Unohana’s healing prowess is legendary. This is first shown when she manages to heal Renji Abarai after his defeat at the hands of Byakuya Kuchiki. She manages to save Renji from certain death, while also delaying her arrival at the Sōkyoku Stand for Rukia Kuchiki’s execution. While attending the execution, Isane Kotetsu expresses open regret that Yamamoto lied to Rukia regarding the release of the Ryoka, but Unohana explain to her lieutenant that despite the harshness of such a lie, it also allows Rukia to die peacefully with the idea that her friends' lives would be spared.

After Ichigo Kurosaki arrives on the scene, destroying of the Sōkyoku stand and starting his battle with Byakuya Kuchiki, the respective captains then head off to their own battles amidst the chaos. Unohana releases Minazuki, even though the actual process is not shown, and saves all those hurt during the initial battle. She keeps Isane with her on top of Minazuki while her Zanpakutō heals the rest of her patients inside of its stomach. Arriving at the Relief Station, Unohana asks Minazuki to release everyone, and seals it back while calling for her surbordinates to tend to the injured personnel for the time being. She then asks Isane to follow her to the Central 46 Chambers.

They arrive at the scene in time to see Aizen defeat Tōshirō Hitsugaya. Captain Unohana annouces her presence to the traitors while citing her own suspicions surrounding Aizen's staged death. She also goes on to claim that the Offices of Central 46 Chambers was the only place he could hide and mentions the use of an elaborate corpse doll on his part. Aizen then points out the mistakes in her analysis, while also commending her for seeing through his deception. The first was that he was not here to hide, and the second was immediately shown as he releases his Zanpakutō in front of Unohana and explains Kyoga Suigetsu's Complete Hypnosis. He then proceeds to tell Unohana about the third member of his group, Kaname Tosen. He and Gin Ichimaru then teleport to Soukyoku Hill, leaving them behind. Unohana immediately requests Isane to find out his exact location, while informing everyone of Aizen’s betrayal, including the ryoka. She then takes steps to save Hitsugaya and Momo Hinamori, both of whom were fatally injured by Aizen before her arrival.

After ensuring that both would escape death for the moment, she leaves them in the care of Isane and travels via Minazuki to the Soukyoku stand, where she tells Yasochika Iemura, the 3rd Seat of her division, that the Ryoka do not require help. She then settles down beside Byakuya Kuchiki and gently scolds him, saying that he has pushed himself too hard. She then calls Rukia over upon Byakuya’s request, during which he reveals his reason for allowing her execution.

A week after Aizen's insurgency, Unohana stops two Squad 11 members from creating a ruckus at the 4th Division’s Relief Station, and unsuccessfully tries to convince Hitsugaya to speak to an unconscious Hinamori, who is still recovering from her injuries.

Hueco Mundo Arc
Unohana and Isane appeared alongside captains Kenpachi Zaraki, Mayuri Kurotsuchi, and Byakuya Kuchiki in Las Noches after the titanic battle between Ichigo and the Espada. Her initial appearance effectively stops the approaching Exequias from doing further harm to Yasutora Sado, in which the leader of the group calmly orders a retreat. She then stops Isane from pursuing them, claiming that they are only there to heal the injured. She proceeds to heal Yasutora Sado and Gantenbainne Mosqueda.

Personality
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. She rarely shows any signs of panic or distress, and has a great sense of duty, shown in the times that she orders Hanatarō’s imprisonment and Isane’s chasing of Abarai when he runs away with Rukia. 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.

Also according to the former captains of the 5th and 7th Division, respectively, she can be very frightening as the look on their faces implied they would never want to get on her bad side (they noted that being destroyed by Shigekuni Yamamoto-Genryūsai's Bankai would be a preferrable fate).

None has ever disputed this fact, for she is an indispensable part of Soul Society and the Gotei 13 Squads.

Powers & Abilities
As the head of the Fourth Division, Unohana is known for her skills in the healing branch of this form of magic. Although she has never been seen in battle, Tite Kubo has stated in one of his Bleach Data Books that her personal specialty is sword fighting, even noting her particular mastery in the Kendo style of fighting.

Zanpakutō
''': In sealed form, Minazuki is slightly longer than an ordinary katana, and resembles a nodachi. Instead of tying it to her obi, Unohana carries her Zanpakutō over her shoulder by a rope strap or lets Isane carry it for her.


 * Shikai:
 * Shikai Special Ability: When unsealed, Minazuki transforms into a giant, flying, one-eyed manta-ray. It is large enough to transport many people on its back (at least a dozen, based on its size when compared to those riding it). Additionally, it can swallow even more people and transport them in its stomach, healing their injuries at the same time. When Unohana reseals Minazuki, it dissolves into green mist and reforms into the sheath of her Zanpakutō.


 * Bankai: Not Yet Revealed