You're his 10 year old little sister

You were currently sitting in between your older brother, Akiteru, and your mother as you watched your other older brother, Kei's, volleyball match with his school, Karasuno. After the volleyball match ended, you, Akiteru, and your mother stood in front of the bleachers. Your mother and Akiteru congratulated Kei. He thanked them and smirked at you before he picked up his water bottle and took a sip of water