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 Grand Fisher was. 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 to 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 are both 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.

Agent of the Shinigami arc
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.

Arrancar arc
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 it's 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 begins talking about Isshin's powers returning and how it is like to be a shinigami again after twenty years. He then proceeds to asks, in a more serious tone, if Isshin has had his revenge, to which Isshin replied that he never really held a grudge against Grand Fisher, but still held a regret that he was not there on that night so many years ago. They then talk about the Vizards' by Urahara questioning if he had noticed that they have contatcted him. The conversation goes on to be about the Arrancar and how the Grand Fisher was by far the most perfect they had seen at the moment and Sōsuke Aizen and his alliances questioning wheter or not the Vizards would take his side or not.

Later when the shinigami Rukia Kuchiki, a friend of Ichigo, needs a place to stay, she lies to Isshin, telling him a sad story about how she has lost everything and needs a place to stay, something both Isshin (seemingly) and Yuzu buys, crying, and resulting in Isshin screaming to the big poster of Masaki that they now have a third daughter.

Hueco Mundo arc
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 are at least on-par or greater 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 are (Zanjutsu, Kidō, Hakuda, and Hohō). However, while he hasn't yet regained his full power, he was powerful enough to bifurcate the imperfect-arrancar Grand Fisher before he realized it. Furthermore, the fact that Kisuke Urahara, a fellow former Shinigami captain, looked to Isshin as his superior implies that Isshin at full strength is a very powerful combatant.

Keen Intellect: While normally appearing goofy and oblivious in his daily life, Isshin has proven to be a highly intelligent man. He has repeatedly shown able to see the truth in any situation placed before him as he immediately realized Kon while in Ichigo's body was not Ichigo and was immediately aware of Ririn, Kurodo, Noba (in the anime), and Kisuke's presence. Isshin has also shown to be a very knowledgable as he already knew about the situation with Aizen and the Arrancar. He is also quite crafty as after discovering his son new status as a Shinigami, Isshin began making preparations to aid his son which including regaining his own Shinigami powers and protecting Ichigo's body with a kido spell.

Expert Hand-to-Hand Combatant: As shown from his repeated comedic attacks on his son, Isshin is a very skilled fighter even when barehanded, further emphasized by how he personally played a part in training Ichigo. Although it would appear that Ichigo has long sinced surpassed Isshin from how Ichigo usually ends up beating his father. Though since its now known that he is at least a captain level shinigami he could be holding back, considering Ichigo initaly wasnt strong enough to fight shinigami captains.

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

Vast Spiritual Energy: As a former Shinigami captain, Isshin possesses a considerable amount of spiritual energy. His spiritual energy is so great that even when not at full power, Ichigo and Shinji were able to sense its strong presence from miles away. As Isshin stated to Grand Fisher, every captain-level shinigami, including himself, must compress their spiritual energy through of their zanpakutō, otherwise, they would be swinging around swords the size of skyscrapers.

Kidō Expert: While it is unknown how well-versed he is in the art, Isshin has demonstrated capable skill in binding spells as shown from enchanting his lucky charm to protect Kon while in Ichigo's body with a barrier powerful enough to prevent a imperfect Arrancar with greater power than an average Gillian from attacking him.

Enhanced Endurance: Even without his Shinigami powers, Isshin appears to have the ability to take severe physical punishment, mostly done through fighting with Ichigo, getting kicked by Karin, and a close range shotgun blast caused by Renji when he was masquerading as a Police Officer.

Zanpakutō
The name of Isshin's zanpakutō has not yet been revealed. It has a red handle and hexagonal handguard. It is also hung from a string wrapped around his belt in an iaidō style, and 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 sealed form 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.
 * It is possible that Isshin's captain-level might is the reason behind Ichigo's naturally high levels of spiritual energy and high growth-rate in shinigami combat as Ichigo may have inherited it from him.