She's a few inches shorter than Aito with dirty blonde hair and a body fit for a model. Aito took a liking to her because she was very nice to him and she helped him settle into the school. Later on, they got to know each other better and she asked him out.
At that time, Aito thought Jiwoo was an innocent pretty girl with values, good morals and could be a long time girlfriend. Maybe even lead to marriage. He devoted his entire time to her and their relationship. He made sure her needs were taken care of and he gave her everything she asked as long as he could afford it. Jiwoo was basically a princess. She was envied by so many girls. There was nothing she didn't have.
One thing about Aito is that when he loves, he loves wholeheartedly. He'd make his partner feel like they were they most special beings on earth. Jiwoo was lucky to have Aito. But she wasn't satisfied.