Ichigo's mother, Masaki Kurosaki, began taking him to a dojo to learn karate when he was four years old. There, he met and fought with Tatsuki Arisawa, whom he lost to the first few times. Whenever this happened, he would start crying, only to stop instantly when comforted by his mother, to whom he was deeply attached. Tatsuki described Ichigo as a thin child, who looked very happy and always smiled when around his mother.
When Ichigo was nine, Masaki was killed by the hollow Grand Fisher, although Ichigo did not find out the true cause of her death until early in the main Bleach storyline. After her death, Ichigo was distraught and stood on the shore where his mother was killed for days. The entire Kurosaki family transformed at the death of Masaki — Karin became tough and did not cry again, while Yuzu took up the household chores. Prior to learning about Grand Fisher, Ichigo felt guilty for his mother's death, blaming himself for wandering too close to the water and causing her to put herself in harm's way to save him. Even after that, Masaki's death continues to influence Ichigo by causing him to feel guilt for his inability to protect those close to him: because of this guilt, Ichigo developed a resolute will to gain the power to protect his loved ones. This is a recurring theme in many of Ichigo's battles, particularly the assertion that his reasoning is the opposite of what he claims: his opponents often claim that he protects his loved ones in order to fight, not the other way around.
Three years before the main storyline, Orihime Inoue's older brother Sora died in the Kurosaki clinic from injuries acquired in a car accident. Ichigo watched as Orihime cried for her brother, although he did not find out that the crying girl he saw was Orihime until a short time before the main storyline.
While in junior high school, Ichigo met and befriended Yasutora Sado, then from Mashiba Junior High, who helped him out of a fight. Ichigo called him Chad because of the nametag he was wearing, which can be read either Sado or Chad, and continued using the name after being corrected. Chad, although extremely strong, was often the target of beatings because he refused to fight for his own sake due to a promise he had made as a child to his grandfather. Upon discovering this, Ichigo made a pact with Chad in which they both agreed to fight and risk their lives for something the other was willing to risk their life for.
Ichigo's spiritual powers are not limited to just shinigami abilities; he possesses hollow powers as a result of his training with Urahara. While attempting to recover his shinigami powers, Ichigo began transforming into a hollow from the corrosion of his severed soul chain. Ichigo succeeds in awakening his shinigami powers, but retains his hollow spirit inside himself from the transformation. The title page of chapter 220 depicts the inner hollow with the mirror writing of Ichigo's name.
Ichigo's hollow spirit is his evil alter ego. The spirit is pretentious and mocks his counterpart's inability in a sneering, didactic fashion whenever the chance arises. He relishes the idea of taking Ichigo's strength for himself, and claims to be the manifestation of Ichigo's instinctive lust for battle and the next kill. He also seems to gain any abilities that Ichigo knows, evidenced by his usage of both getsuga tensho and bankai. Unlike Ichigo, the hollow fights like a berserker, and is able to ignore any injuries Ichigo has previously sustained along with considerable increases to his speed and strength.
At different points in the series, Ichigo's hollow powers have manifested themselves in different ways. Initially, Ichigo's hollow mask would appear on his body to block fatal blows, unbeknownst to Ichigo until the fight ends. During his battle with Byakuya Kuchiki, half of the mask appeared on his face when Byakuya was about to get the finishing blow, allowing his inner hollow to take over until Ichigo suppressed it. The same event is repeated multiple times after that, first indication of which being Ichigo's left eye gradually blackening, as the hollow takes control. While suppressing his inner hollow, Ichigo is left effectively paralyzed, since his concentration was focused on suppressing it rather than fighting. The hollow claims that it manifests itself to protect Ichigo during near death moments because it is connected to Ichigo, and it would be a great inconvenience to the hollow if Ichigo was to die.
While he was in training with the vizard, Ichigo's soul was completely overcome by his inner hollow for a short period, causing him to physically transform into a hollow. His near-complete hollow form resembles a large, humanoid lizard. In this form, Ichigo demonstrated several high-level abilities, including high speed regeneration, enhancement of limbs, and the ability to fire cero blasts from his fingers. However, this form didn't last long as Ichigo emerged from the hollow shell as his standard shinigami self wearing a hollow mask.
After training with the vizard and subjugating his inner hollow, Ichigo can use his hollow mask while retaining his personality, but could originally only wear it for eleven seconds at a time. His limit increases during his third battle with Grimmjow Jeagerjaques, but to what extent is unclear. His overall limit is barely a fraction of the amount other vizard can maintain their masks. After the time limit, the mask breaks and Ichigo loses its benefits. Subsequent attempts to use the mask can only be maintained for an instant. While wearing the mask, Ichigo's hollow powers supplement his shinigami powers, giving him a vast increase in both strength and speed.