Isane Kotetsu

is the lieutenant of the 4th Division, the medical and supply relief division, in Gotei 13 under Captain Retsu Unohana.

Appearance
Isane is a tall woman and has short silver hair. Some of her hair is braided on one side of her head. She wears a standard Shinigami uniform with her lieutenant badge on her left arm.

Personality
"The delicate Lieutenant that does not seem as such from her appearance. She cannot sleep after getting a nightmare. Kamaboko?" - picture caption by Tite Kubo

Isane is the older sister of Kiyone Kotetsu, one of the two 3rd seated officers in the 13th Division. Unlike Kiyone, she is generally quiet and observant, though she shares her sister's sense of loyalty. However unlike her captain, she can be impatient in the face of an enemy, rushing after enemies she has no chance of defeating, including the seemingly unstoppable Sōsuke Aizen. She looks to Unohana as a mentor and mother figure. It is noted by Unohana that Isane suffers from frequent and recurring nightmares. This is sometimes used as material for jokes, as Isane's nightmares are often odd or whimsical in their contents. For example, she once had a nightmare involving kamaboko (a fishcake made of pureed surimi), which she intensely dislikes. Her favorite food, on the other hand, is porridge, to the extent that she is capable of eating it as the three main meals on the same day.

Isane's exceptional height for a female Shinigami is often material for jokes. She started eating porridge when she passed 170 cm in her growth, because she did not want to get any taller (she believes - wrongly - that the nutrient level of porridge is very low). Unfortunately for her, she did not stop until reaching 187 cm, her height being another source of frustration for her. Her height is also mentioned on one of the assemblies of the Shinigami Women's Association, during which she proposes a cell phone sturdy enough to not break if it is dropped from a height of 2 meters, only to be told by Nanao Ise that it is not a common problem. Once, after hearing of how sleeping helps children grow, she decides to not sleep again in order to halt her growth.

When Isane has time off, she goes to see Kiyone, and when Kiyone has time off, she goes to see Isane. They're very close sisters who enjoy meeting up and having fun together. Recently, her favorite place to hang out is the Kuchiki estate, in the "secret base of the Shinigami Women's Association". She is a notable member of the latter Association, where her meek nature occasionally gets her in troubles with group activities including getting captured alongside Nemu Kurotsuchi when attempting to take a picture of Byakuya Kuchiki.

Soul Society arc
Isane is mostly seen around Retsu Unohana. When Hanatarō Yamada went back to the 4th division after he met with Jūshirō Ukitake, he gets in trouble with his Captain. However, when Isane is walking with him afterwards, Hanatarō asks if what he had done was wrong, and Isane answers he was brave for what he did.

Isane attends the execution of Rukia Kuchiki with her captain on the Sōkyoku Hill as well as her rescue by Ichigo Kurosaki. She appears upset by Genryūsai Shigekuni Yamamoto's false promise to allow Rukia's would-be rescuers to leave safely after her execution, but Unohana tells her that he said it so she could die in peace. After Rukia is handed off to Renji Abarai to get away, Isane hesitantly joins with Chōjirō Sasakibe and Marechiyo Ōmaeda after them. She releases her Zanpakutō to fight against Ichigo Kurosaki, but is taken down much lighter than the other two. After her defeat, her sister Kiyone runs over to aid her, but Soifon intercepts her and knocks her to the ground. If not for the fast action of Yoruichi Shihōin, Kiyone would have been killed.

Unohana picks up Isane, and when she starts to apologize for failing to defeat Ichigo, Unohana tells her to calm down. After dropping the wounded off, Isane and Unohana quickly head to Central 46. They arrive at the scene in time to see Aizen defeat Tōshirō Hitsugaya. Captain Unohana announces 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. Isane learns of Sōsuke Aizen's betrayal, and reveals that she and the other lieutenants thought Kyoka Suigetsu was a running water-type Zanpakutō, not one with the ability of perfect hypnosis. Isane prepares to attack Aizen, but he and Gin Ichimaru quickly get away before she can get near them. Unohana then instructs Isane to use her Kidō skills, both in tracking down Aizen and communicating with the remainder of Soul Society on the emergent schemes of the traitorous captain, as well as the Ryoka.

After the end of the incident, Isane assists the rest of her squad in healing the wounded. In the middle of the night, she wakes up while having a nightmare about fish paste. She wanders out to get some air while trying to decide what to do, only to be discovered by her Captain, who gently tells her to get some sleep. .

Bount arc
Isane makes several minor appearences in the Bount arc, notably along with her Captain and Iemura healing wounded soldiers and later informing Toshiro Hitsugaya of updates during Jin Kariya's invasion of the Seireitei.

Hueco Mundo arc
Isane arrives in Hueco Mundo with her Captain, Hanatarō Yamada, Byakuya Kuchiki, Kenpachi Zaraki, Yachiru Kusajishi, Mayuri Kurotsuchi, and Nemu Kurotsuchi. When Isane and Unohana arrive, they are met by Rudobōn and the Exequias, who flee after hearing Retsu Unohana is a Captain. Isane prepares to chase after them, but Unohana stops her. She and Unohana proceed to heal Yasutora Sado and Gantenbainne Mosqueda. She later tracks down Byakuya's location and does not appear until after his battle with the 7th Espada Zommari Leroux. She then proceeds to heal Hanatarō and Rukia.

Powers & Abilities
Kidō Expert: Isane is shown to be highly proficient in kido spells, apparently excelling in chaining multiple spells together for various effect. While being the second most proficient in healing Kidō in the 4th Division, she has good understanding of binding spells as well.

Expert Healer: As the lieutenant of the 4th Division, Isane excels in healing techniques, being second in the 4th Division, only to her captain. Known for speedy skill in giving medical attention.

Flash Steps: Isane is proficient enough in flash steps to keep up with her captain.

High Spiritual Energy: Being a lieutenant of the Gotei 13, Isane boasts a high spiritual energy.

Zanpakutō
. A katana with a deep blue handle and a pointed round guard, somewhat similar to a snowflake. It is kept sheathed on the left side of Isane's waist.


 * Shikai: Its Shikai command is . When its Shikai is activated, two smaller blades protrude from Itegumo's hilt at 45° angles.


 * Shikai Special Ability: Unknown


 * Bankai: Not Yet Achieved

Trivia

 * Isane was one of three Lieutenant-level Shinigami that Kurosaki Ichigo defeated bare-handed with a single attack. The other two are Chōjirō Sasakibe and Marechiyo Ōmaeda. To date, this has been the only time that a Lieutenant-level Shinigami has been defeated with a single attack from an opponent.