Isane Kotetsu

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

Personality
"The delicate vice-captain 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, she did not stop until reaching 187 cm, her height being another source of frustration for her. Her height is also mentioned in the Shinigami Women's association omake, in 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 that it is not a common problem. In Episode 194's Shinigami's cup, after hearing of how sleep helps children grow, decides to not sleep again in order to halt her growth.

Outside her unit, Isane spends her time either with her sister or with other female shinigam, the most popular venue being the Shinigami Women's Association's secret hideout in the Kuchiki estate. 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 was mostly seen around Retsu Unohana. When Hanatarou went back to the 4th division after he met with Ukitake, he got in trouble by his Captain. however afterwards Isane was walking with him Hanatarō Yamada asked if what he done was wrong, Isane said he was brave what he done.

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 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 her, but Soifon intercepts her and knocks her to the ground. Yoruichi Shihōin saves Kiyone, though.

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, the two 4th Squad leaders quickly head to Central 46. Isane learns of Aizen's betrayal, and reveals that she and the other lieutenants thought Kyoka Suigetsu was a running water-type zanpakuto, 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 her 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.

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.

Hueco Mundo Arc
Isane arrives in Hueco Mundo with her Captain, when they get there they are met by Rudobōn, who flees after hearing Retsu Unohana was a Captain, Isane went chasing after him, but was stopped by her captain. She then appeared after the battle between Byakuya Kuchiki and Zommari Leroux to heal Hanatarō Yamada and Rukia Kuchiki.

Powers & Abilities
Kidō Expert: as the lieutenant of the 4th Division, Isane excels in healing type Kidō.

Healer

Zanpakutō
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 * Shikai: Its Shikai command is . The guard is shaped like a snowflake. When its Shikai is activated, two smaller blades protrude from Itegumo's hilt at 45° angles. She is never seen using it in combat, since the one time she activates it she is immediately knocked out by Ichigo Kurosaki, although some fans speculate that due to its name and guard shape, Itegumo may have the the ability the manipulate ice and snow.


 * Bankai: Not Yet Achieved