From the looks of it, Koyuki, our protagonist, was bullied and teased relentlessly in elementary and middle school. She was even ostracized because a girl got jealous. Even now, jerks will target her (though this will likely happen to any girl or woman just trying to mind her business in public). As a result, she has developed a defense mechanism; she projects an icy exterior that keeps others away. I’m glad the series decided to literally show us what the rampart might look like. Y’know, just in case the metaphor hasn’t sunk in.