Daisaku Daimon starts as the coach for Hikawa Junior High's girls' volleyball team, enforcing severe and physically abusive methods. He strikes players with a bamboo sword and slaps them for mistakes, however minor, or even after victories, leading to his removal from Hikawa.

He identifies athletic potential early, recruiting protagonist Mila Hazuki upon noticing her natural jumping ability. Over time, Daimon builds professional connections with key athletes, later coaching Nami Hayase at the Unicorn team post-Hikawa.

His career advances to the national level, coaching Japan's women's volleyball team. Assigned to lead Team B in internal competitions against coach Yamahoka's Team A, these matches decide Olympic player selection priorities.

Daimon's philosophy stresses extreme discipline and physical rigor, sparking initial friction within teams. His methods nonetheless develop several elite players who reach national and international competitions.