Kaori Miyazono is a free-spirited violinist whose playing style reflects on her personality. She is Independent, unpredictable, and short-tempered.
While considered a really sloppy violin player from a technical standpoint such as not following music score sheets the way they are written, Kaori is an amazing violinist. Noted by one of the judges at Towa Hall during the first competition of the series, her pure abilities far exceed the others in the competition. She wields a free spirited style of performance that emphasizes emotions and artistry over the pure mechanics of music such playing to specific tempos and dynamics originally intended by the composer. Her style of music is what inspires Kōsei, to regain a passion for the piano and redefine himself as a musician.
Kaori's parents own a bakery shop that further develops her happy go lucky, free spirited personality. It is often shown that Kaori loves children and is often seen interacting with kids about music. Kaori also appears to be hiding some type of illness when she collapses during her first performance with Kōsei. While she claims to be anemic, there seems to be a deeper health concern as Kaori was unable to participate in her callback round with Kōsei due to being hospitalized.
from Wikia