Hajime Iwaizumi (Japanese: 岩泉いわいずみ 一はじめ, Iwaizumi Hajime) was a third-year student at Aoba Johsai High. He was a wing spiker, ace and vice-captain for the boys' volleyball team. He is Tōru Oikawa's childhood friend. After graduating high school, Iwaizumi went to college and majored in sports science. In 2021, he is an athletic trainer and is seen working with the Japanese National Volleyball Team.