Kenma's Sister ( Haikyuu X OC )

Kenna

Kozume Kenna.

Since birth her health was delicate. It wasn't her parents fault it was just one of those things that happen.

So her parents decided she stay indoors. Her older brother Kenma was her only friend. Only a year older they got along just fine. Then school started up. Kenma would be gone for hours and she had nothing to do. Both were always relieved when he came home. Since he wasn't used to people and she missed him.

Bored while Kenma is gone she took up video games which she showed to him when he got home. Now both siblings were addicted to them. Their parents even let her go outside to buy games if Kenma was with her. She can be allowed outside for a certain amount of hours per day now.

Then around the time she was 7, new people moved into the house next to them. That's the first time she met Kuroo.

He was Kenma's age and a little shy like both of them. He came over to the house a lot so they taught him how to play video games. Kenna was happy to have another person in the house.

But again she would have to lay back.

She convinced Kenma to leave her and go with Kuroo to the kids volleyball group cause she knew he secretly wanted to join. She encouraged him to keep on going whenever he was wary because she would be left alone. She helped him when he was at home thinking up different strategies and became his number one fan. She grew to love the sport that was helping her brother gain friends. 

She showed up to all his games and would become an unofficial manager to his teams. The famous Kozume duo.

Then one day while at the doctors she realized it would be better for her to live outside of Tokyo. It would lower her chances of catching something and help take the stress of her family. 

She was about to enter high school anyways and thinking about Kenma she realized this is a perfect opportunity for her to leave Tokyo and give Kenma freedom from her. So she spoke with her parents and the Doctor all agreed for her to move to the Myagi Prefecture where she will attend high school.

She didn't say bye to Kenma or Nekoma (who she was always with) knowing they would stop her and she left. Kenma was not to know of why she left and if he asks why he will only be told, she was recuperating.

This is how Kenna meets the Karasuno Volleyball team.