Akimitsu Bizen directs and coaches the water polo teams at Shogakukan Middle and High School. He possesses a lean, athletic frame, fair skin, short black hair with a widow's peak, dark gray eyes, slight facial hair, and age lines befitting middle age, typically dressed in business casual attire.

His coaching philosophy demands victory through a single dominant ace player, viewing all others as replaceable tools. He explicitly disregards players' emotions and humanity, seeing them solely as instruments for winning. This includes instructing the ace to humiliate teammates over minor errors to maintain control, irrespective of their effort or improvement.

These methods profoundly altered Minato Kiyomizu, transforming the kind, outgoing athlete into an aggressive, isolated individual. Akimitsu compelled Minato to abandon his compassion, fostering a mindset where teammates and family became rivals. After Minato regained memories lost in a coma, Akimitsu dismissed him from the team, citing his year-long absence and implying the accident causing the coma was Minato's failure, reinforcing his view of players as expendable.

He applies identical tactics to Shogakukan's current ace, Riku Momosaki, training him to become an egoist. Despite Riku's skill progression matching Minato's former level, Akimitsu refuses to acknowledge his accomplishments, criticizing every minor error and asserting Minato's superiority.

His background is largely undefined, though his name—Akimitsu (昭充: "shining, bright" and "allot, fill") and Bizen (備前: "equip/preparation" and "front/former")—reflects themes of control and instrumentality. His methodology remains consistent across all events, prioritizing victory through psychological manipulation and dehumanization without development or remorse.