Yusuke Okuma (大隈 優介, Okuma Yusuke) is a second-year student of Seiin High School who serves as a middle blocker on the boys' volleyball team.
Okuma has blonde hair slicked back from his forehead and brown eyes. He stands at 187 cm (6'1").
During matches, Kimichika Haijima wears his volleyball uniform – a navy blue jersey with sky blue and white stripes on the sleeves and corresponding navy blue shorts. His position number, 10, and the name of the school are printed on the front of his jersey in sky blue text with a white outline. On the court, he wears white kneepads and white volleyball shoes with black accents.
Okuma is a former member of the rugby team who was invited to the volleyball team by the vice captain, Misao Aoki.
- The name Yusuke means "excellence, superiority, gentleness" (優) (yu) and "forerunner, herald" (介) (suke).
- Yusuke's surname Okuma means "big, great" (大) (o) and "corner, nook, recess" (隈)(kuma).
- Okuma was initially a member of the Seiin rugby team. However, Misao Aoki offered him a position on the volleyball team after seeing his performance during the school's sports festival.