Shortly after she and her brother were born, their parents separated, and she was taken to live with her father in Orre for many years. Her father wasn't the best person, so she spent most her time exploring Orre, despite it being a boring yet dangerous desert. She was eventually given an Eevee to at least have a Pokémon to protect herself with, as she was a mischievous kid. Eventually she was sent back to live with her mom (and Iori) in Kanto. She didn't understand any sign language at first, so she was frustrated for awhile, somehow feeling more isolated than ever. Eventually, Kaori became friends with Shigeru since she at least had decent Japanese, but overtime she still became more withdrawn and odd. While being less interested in the League than the boys, she doesn't want to be left out, so follows their plans of taking it on. She mostly is interested in seeking out rare Pokémon, particularly one connected to a strange lab accident...
Her dedication to finding Mewtwo gets the attention of a cute young girl named Yellow, who is also interested in looking for him.
In LGPE, she's the dedicated Himemi harasser who is also chasing after Mewtwo still.
Haruna (始菜) is some sort of traveller like her brother, Haruo. Some sorta less-serious ronin. She frequently crossdresses as him, though he doesn't realize this. She finds a way to weasel her way into the royal court to protect all the fine ladies there.
Kaori stalks Iori to find what hick village he moved to, and opens up a café there.