Isshin Kurosaki

is the biological father of Ichigo, Karin and Yuzu and as such, head of the Kurosaki family. He runs their private clinic, the Kurosaki Clinic. A skilled doctor, Isshin can perform almost any medical procedure except major surgery. Initially, Tite Kubo wanted to portray Isshin as a mortician, rather than a doctor, because Kubo thought Isshin looked better in a black suit.

Character outline
In the beginning of the series, Isshin is portrayed as a silly, fight-loving father who is "extremely over-energetic" and takes a keen interest in what his children are doing, but does it either offensively or with an all-too-happy tone, which elicits comical reactions from his kids, usually in the form of a kick. Because his kids choose to keep to themselves, he doesn't know what they are doing. Mainly Ichigo, but since he's a boy, Ichigo doesn't need to be watched over as much as his twin daughters. Isshin also seems to enjoy making fun of Ichigo and has a tendency to talk to the large memorial poster of his late wife Masaki, which he has pinned up in their kitchen, whenever he feels particularly emotional. Isshin is a big fan of Don Kanonji's TV show.

Despite his outrageous guise, however, Isshin can be serious and grim at times. On the date of Masaki's death, Isshin smokes a single cigarette in front of her grave, since she thought it made him look cool (she said it when they were dating). He reflects that it was the first and maybe the last time she ever complimented his appearance. He also told Ichigo that he shouldn't blame himself for his mother's death because she gave her life to protect him. In addition, during his confrontation with the arrancar Grand Fisher and the subsequent chat with Kisuke Urahara, he remains completely serious (aside from a short argument between him and Kon about his parenting, and another, albeit short, between him and Urahara after the latter likens him to his son).

Isshin appears to be an associate of Kisuke Urahara and possesses knowledge of Sōsuke Aizen's alliance with the Menos. He mentions in his conversation with Urahara that he encountered arrancar about ten years before the main storyline, though they were nowhere near as complete as Fisher. He also reveals to Kon that he has been aware of Ichigo's shinigami activities and Kon's substitutions since Grand Fisher's first attack. He also notes that he has never called Kon "Ichigo" while Kon is in Ichigo's body and that the traveling charm he gave Ichigo before he went to rescue Rukia was actually for Kon (it's a protection talisman). This shows the sensitivity and propriety that he possesses of his role as Ichigo's father, which is rarely portrayed in the series.

Isshin also shares a relationship with Ryūken Ishida not unlike that of their sons. When Ryūken discovers his son is missing, Isshin pays him a visit and the two chat about their respective styles of parenting. It is then revealed that Ryūken was aware of Isshin's status, and he comments on Isshin's powers. The Bleach Official Animation Book VIBEs states that the two have some prior history together, and that they have been acquaintances for quite some time. It can also be noted they both are doctors, Isshin runs a clinic while Ryūken runs a hospital. It was hinted in volume 1 that the two cooperate on a professional level. After a major car accident, Isshin is overheard on the phone arguing with a hospital employee who is refusing to transfer the overload of patients. He says that the employee should tell his boss that Kurosaki needs a favor and then beds will open right up, then slams the phone down.

History
Little is known about Isshin's history, except that he was once a captain-level shinigami, though his division is currently unknown. Twenty years before the main storyline, he ceased being a shinigami, although it is unclear whether he officially quit his duties at that time or on an earlier date. His current shinigami uniform retains a captain's robe, but it has no visible division insignia and is worn like a sash over his left shoulder. After leaving the shinigami, Isshin lost most of his powers, and has only recently regained them. It is implied that he was more powerful and is still recovering. However, he was still powerful enough at this point to slay Grand Fisher, in his released arrancar form, with a single strike of his sealed zanpakutō.

He married Masaki Kurosaki and they had three children: Ichigo, Karin and Yuzu. Masaki later died at the hands of Grand Fisher, who was a simple hollow at the time, six years before the main storyline. Isshin was unable to prevent Masaki's death and blamed himself for it; later in the series however, he eventually kills Grand Fisher, both protecting Kon (inhabiting Ichigo's body) from attack and finally avenging his wife's death.

Synopsis
Isshin plays the role character since early in the story, often attacking Ichigo or annoying his daughters. In the first episode it appears that he has no clue whats going on in Ichigo's life since he didn't know that more and more souls had been talking to Ichigo, something that Ichigo had told his sisters. Secretly, however, he has had complete knowledge of Ichigo's shinigami activities. He also knows about Kon, who takes Ichigo's place when he's gone, and never once has called Kon "Ichigo" while he's in his son's body.

Isshin gives Ichigo a talisman, claiming it's a good luck charm originally given to him by Masaki, when really it was to protect Ichigo's body while Kon is in it. Isshin also has a brief fight with Grand Fisher, where he kills the arrancar with a single cut from his sword, thereby avenging his wife's death. When Grand Fisher says that the size of a sword shows the amount of power someone may have, Isshin states that while its true, captain-level shinigami know to compress it, otherwise all captains of the Soul Society would be swinging around swords the size of skyscrapers. Urahara then appears, and they talk about the Vizards' interest in Ichigo and Sōsuke Aizen. When Ichigo leaves for Hueco Mundo, Isshin visits Ryūken at the hospital, commenting on what a horrible father Ryūken is and also accepting the fact that he himself is a horrible father. He was able to get into the underground training spot even though Ryūken mostly hid it. His old friend is genuinely surprised that Isshin has regained his powers, while Isshin notices that Ryūken still smokes despite being in a hospital.

Powers & Abilities
When Isshin first appears in his shinigami uniform, he implies that he has abilities on-par to that of a Captain-level shinigami. This is further implied by the fact that he has a haori strapped to his left shoulder as a type of strap. It is unknown what the extent of Isshin's shinigami powers is (Zanjutsu, Kidō, Hakuda, and Hohō). However, he was quick enough to bifurcate Grand Fisher before he realized it.

Master Swordsmanship Specialist: The only seen fighting once and for a few seconds, Isshin's skill in swordsmanship allowed him to effortlessly slice through Grand Fisher's giant zanpakuto without losing any visible momentum and still cut down Grand Fisher in the process with only his sealed zanpakuto.

Zanpakutō
The name of Isshin's zanpakutō has not yet been revealed. Isshin has only used it once as an example of how every captain-level shinigami must compress the sizes of their zanpakutō, as they would otherwise be swinging swords the size of skyscrapers, when he spoke to Grand Fisher. It is also worn with the edge down like a tachi, instead of the edge up like a katana. The end of the hilt has a tassel similar to Ichigo's original zanpakutō.


 * Shikai: Not Yet Revealed


 * Bankai: Not Yet Revealed

Trivia

 * Numerous fans now believe that Isshin was previously captain of 3rd Squad before Rose's captaincy. This is fueled by Shinji's mention that the captain before Rose had retired.
 * However, Urahara said that he gave up his Shinigami powers 20 years ago, which wouldn't fit if he stepped back as a captain 100 years ago. Also, it is implied that he doesn't know the true origin of the Vizards and that he only has heard of them, and furthermore, Shinji didn't recognize his reiatsu, which he should have if he was a captain in his time.
 * It could be that he had been the captain of 10th Squad before Tōshirō Hitsugaya, as it would fit the fact that he, as mentioned before, lost his Shinigami powers 20 years ago, and that Hitsugaya became a captain not long after that.