The refined Yukino is merely a camouflage to disguise her true intentions. She may seem easy going and laidback, but in reality, she's an ultra-perfectionist and can't stand not being on top. Adoration and fame are her life force, and she'll destroy anything that threatens her position.
But that all changes when she meets Arima. She's still very competitive, but she slowly learns to show her real side and be happy with her true self.
It all began in kindergarten. Being an oldest child, Yukino was used to taking care of others, and adults praised her for being so smart and dependable. She loved hearing those sweet words, and wanted to hear more. She wondered, "if I could learn more... get the best grades... be the class leader..."
And so, the ever ambitious Yukino began her quest to be the best, and she soon mastered the art of fooling those around her. She knew she had to be perfect to get to the top, and quickly rose above the rest, careful not to let her mask slip.
She didn't care about love, friendship, or trust. She was simply focused on one goal: to make herself seem even more wonderful to everyone else. Yukino thought she was the smartest girl in the world, for living the way she was. But deep down, she was really miserable.
Yukino is easily the most popular girl in school. She has many friends, but none of them are true friends, because being at the top kind of isolates her. And besides, Yukino didn't want them getting too close to her, for fear they would find out her true self. This is also why she never had a boyfriend before.
When students needed help on their homework, Yukino was there to teach them. Teachers loved calling on her because she was so studious and dependable. Guys loved her because she was so pretty and smart. Girls loved her because she was so sweet and friendly.
On top of her tough schoolwork and studying, she is on billions of school committees and stays in school for long hours. But she doesn't mind the workload, because she always worked hard, so she was used to it.
She dreams of becoming a high-ranking executive or a lawyer, because she loves the power and elitism. And of course, she loves the challenge and victory.
Her family are the only ones that see the real Yukino. At home, Yukino switches out of her "refined" mode and becomes the lazy, stubborn, and rude girl that she really is. As she once explained, where else was she going to relax?
She comes from a middle income, tight-knit and loving family. Yukino is quite embarrassed about her weird (and hiliarious!) family, and they love poking fun of her. She and her sisters are very close, and although they are younger, sometimes they act more mature. They give Yukino advice and help keep her grounded.
Although Yukino is the ultimate narcissist, she can be very mature and selfless. For example, she has the brains to get into any top private school of her choice, but she chose to go to Hokuei Prefectural High School, a top public school in her area. She explains that her family isn't that wealthy, and she also has two younger sisters going to school, so she didn't want to become a financial burden on her parents.
Everything was going according to her plan, until she entered high school and had her top spot taken by Arima. He was like her in every way - smart, good looking, athletic, kind... Except, he seemed genuine about everything. But she couldn't forgive him for taking her spot, and obsessively plots to bring him down.
He was her new goal, and she was determined to win. She finally gets her chance when Arima confesses his feelings for her, and simply brushes him off. But soon after, she gets caught by Arima in her true, dorky form.
She was soon blackmailed into becoming Arima's servant, fearing he would tell the others the truth about her not-so-perfect personality. But the more she hung out with Arima, the more she realized she was falling in love with him. After a rocky start, they finally become boyfriend and girlfriend.
Yukino is used to having others depend on her, but with Arima, she learns that its ok to depend on others. Most importantly, she knows that he loves her for her.