"During her childhood, she is portrayed as a cheerful, friendly little girl who loves to play and hang out with her friends. However, due to her naturally naive personality, she tended to blurt out the thoughts of other children which they prefer to keep a secret, causing misunderstandings between people around her. As a result, she became isolated and developed a cold personality that shuts out others, being generally rude" 

( http://kotoura-san.wikia.com/wiki/Haruka_Kotoura )