Unohana Retsu

Captain of the Fourth Division. A woman with a calm appearance, characterized by her hair styled in a single braid at the nape of her neck. She refers to herself as "watashi." Generally, she is a quiet and gentle person, but she can intimidate patients who don't listen to her or those who don't follow her opinions with a smile. She was once taught recovery and healing Kido and Kaido by Kirinji Tenjirou of the Royal Guard. As the head of the healing department, she doesn't often go to the front lines and mainly plays a supportive role within the division. However, due to her background, she originally has a talent for combat. Incidentally, she is a veteran captain second only to Yamamoto, whom Kyoraku refers to as "great senior," and is a rare captain who can express her opinions to the head captain, Yamamoto.

During the commotion in the Soul Society arc, she was the only one who sensed the faint unnaturalness of Aizen's "corpse" and, like Hitsugaya, quickly recognized Aizen's plot, allowing the Shinigami side to take swift action. In the Arrancar arc, she infiltrated Hueco Mundo along with Byakuya, Kenpachi, and Mayuri, provided medical aid to Sado and Gantenbain, and then accompanied Ichigo as he rushed to the World of the Living. On the way to the World of the Living, she explained Aizen's Kyoka Suigetsu ability to Ichigo, healed his body and spiritual pressure wounded in the battle in Hueco Mundo, and after reaching the World of the Living, she treated the injured Hiyori and others.

In the Thousand-Year Blood War arc, it is revealed that her real name and the fact that she was the first "Kenpachi" are discovered. Her real name, "Yachiru," was self-named from her pride in mastering countless swordsmanship styles, and she was once an unprecedented criminal in the history of the Soul Society. However, Yamamoto recognized her power and appointed her as the captain of the Eleventh Division, laying the foundation for the current Eleventh Division. During that time, she met the young Zaraki Kenpachi, and they both sought stronger opponents, engaging in a battle that exhilarated them. However, during the fight, Kenpachi unconsciously feared that "if he killed her, he would never enjoy a proper fight again," and suppressed his power to match the weaker Unohana. Despairing at her own inadequacy for sealing Kenpachi's power, she simultaneously became convinced that he was the one truly worthy of the name "Kenpachi."

After the first invasion by the Sternritter, she received the new head captain Kyoraku's instruction to "teach Zaraki Kenpachi swordsmanship" and engaged in a deadly battle with Zaraki Kenpachi in Muken. Satisfied with having awakened his abilities, she fell before his blade and died. In the "Hell Verse," she, along with Yamamoto and Ukitake, was targeted for the Soul Funeral Festival, which sends souls to Hell, and her epithet "Shiken" was revealed.

[Zanpakuto]: Minazuki

The release command is unknown. Upon releasing its ability, it transforms into a large ray-like creature that exhibits healing abilities on those it swallows. In its sealed state, it has a significantly curved blade compared to a normal sword and comes with a shoulder strap. In its sealed state, it is usually carried by Isane unless something significant occurs.

[Bankai]: Minazuki

Although the kanji differ from the Shikai, it shares the same name. Upon releasing its ability, a blood-like liquid drips around, forming a blade that seems to converge on the sword. The detailed ability is unknown. According to the anime depiction, it appears to "cut the enemy with the sword, absorb the blood oozing from the enemy's body, and continuously heal one's own wounds." In the game "Brave Souls," after launching a slash, it has the effect of healing all allies' health and dealing damage to all hit enemies.