Bleach features a massive cast of characters and has managed to develop nearly all of them over time -- even incidental side characters. This includes many of the Soul Reapers whom Ichigo and his friends meet during the Soul Society story arc, like the oddly cute and tiny Lieutenant of Squad 11, Yachiru Kusajishi.
Squad 11 is the most brutal and honor-bound of the 13 court guard squads in the Soul Society, led by the fearsome Captain Kenpachi Zaraki. The likes of Ikkaku Madarame could have been Lieutenant, but that rank instead went to Yachiru, whose youth, appearance and personality subvert all expectations of a Squad 11 officer. Here's her story in Bleach, and her unique role in her foster father's life.
When Yachiru & Kenpachi Crossed Paths
Little is known of Yachiru's family or the circumstances of her birth in Bleach. Her first appearance in a flashback depicts her as a downtrodden urchin in the 79th district of the Rukongai, likely an orphan or simply abandoned. Yachiru was very young, yet seemed oddly relaxed despite her extreme circumstances and vulnerability. Around this time, the pre-Soul Reaper Kenpachi happened upon the pink-haired youth while wandering about, thinking little of her at first. But he was wrong -- she had unexpected strength of spirit and did not fear the towering Kenpachi or his ragged zanpakuto. In fact, she once touched the zanpakuto as though it were a toy, which made an impression on Kenpachi.
He named the girl Yachiru, after the Soul Reaper Captain who had defeated him in combat in his boyhood. "Kusajishi" was the name of the district where Kenpachi found her, and thus Yachiru Kusajishi became his companion during his travels. When he became a Soul Reaper, Yachiru tagged along and even earned the rank of Lieutenant to stay by his side. Despite her size, youth and background, Yachiru had the necessary technique and spiritual strength to attain her rank fairly, and every member of Squad 11 has learned to respect her as their superior. Yachiru, however, is more than Kenpachi's little companion. She is the very source of his strength.
Yachiru's Surprising Strength & Vital Role In Captain Zaraki's Career
Yachiru Kusajishi rarely fights and instead watches as Kenpachi does so, cheering him on or simply making comments on the battle. Kenpachi won't readily admit it, but Yachiru is precious to him, and even his bloodlust isn't as strong as his protective instincts. Anytime Yachiru is threatened in combat, Kenpachi will fly into a rage, pushing himself to new heights to defend her. During Bleach's Hueco Mundo story arc, the 5th Espada Nnoitora Gilga tried to dispatch Yachiru, only for a wounded Kenpachi to get back up, swing his sword, and take one of Nnoitora's four arms off. Yachiru herself explained that Kenpachi "gets mad" when people attack her, a statement he tried to deny.
The young Yachiru is powerful in other ways too. Despite her youth and inexperience, she was once the Soul Reaper Women's Association's president and ordered the other members around to satisfy her every whim. It's remarkable that Soul Reapers such as Nanao Ise, Isane Kotetsu and Rangiku Matsumoto obeyed without question like that. Most likely Yachiru intimidated them and/or threatened to bring in Kenpachi if she doesn't get her way. Despite this, Yachiru's goals are juvenile: pulling pranks, getting candy and finding toys to play with. And she has every member of the Women's Association to help her out.
If Yachiru must fight, she can attack and defend entirely on reflex with abilities rivaling any Soul Reaper Lieutenant in Bleach. She can also easily intimidate other Squad 11 members with her intense spiritual pressure and glare, and doesn't respond well to criticism. Squad 11's members soon learned to fear and respect her almost as much as Captain Zaraki himself.