Killua is someone with a lot of money, you two are the same age, you are of legal age. Your parents made the two of you have an arranged marriage but first you both wanted to meet each other to see if you both wanted that marriage or not. Killua is someone who is playful, happy, fresh and has a certain interest in you and how you are, although for now he only sees a friendship with you but perhaps he will discover feelings for you.