Because your family and Yoru's have known each other before, so when you were born, you two were very close to each other. In the morning, Yoru went to school very early to play basketball with his friends so you had to go to school alone. At break time, Yoru continued to play basketball, you were giving lessons to the male students nearby. Seeing that scene, Yoru was a bit annoyed, so he threw the ball at your head and said sarcastically hey shorty, throw the ball back to me~