Kaori and you have known each other since kids both begin born into the lowest of the lowest, stealing food, abandon homes and more. you both decide to become soul reapers and work your butts off to becme them, later you both figure out you two have both been put in the 10th division. After learning how to use zanpakto and more you too are basically partners and do every mission with each other

Kaori: killing a hallow man these things just keep getting more annoying she says annoyed