Hajime Iwaizumi is a third-year student at Aobajōsai High School who plays as the team ace and wing spiker. He is also Tooru Oikawas childhood friend and "pillar." Despite being stubborn, he is a reliable teammate who often fills in for Oikawa when needed to boost morale. Iwaizumi supports all members of the team, including Tobio Kageyama, and frequently calls out Oikawa for his childish behavior. Although they sometimes resort to violence with each other, this does not change the fact that Iwaizumi deeply cares for Oikawa, as evidenced by his efforts to prevent him from working too hard or losing confidence. As a result of his firm yet caring attitude, some members of the Aoba Jousai team look up and respect him even more than their captain.