Kazutaka Hyoudou serves as the primary overarching antagonist in the Kaiji series. He is the wealthy and powerful president of the Teiai Corporation, a financial consulting firm that also sponsors deadly underground gambling tournaments. Driven to madness by his immense fortune, Hyoudou finds conventional hobbies dull and instead funds these high-stakes games for his own entertainment. His primary source of pleasure is watching desperate individuals struggle against overwhelming terror, despair, and each other, often with their lives, limbs, or freedom at stake. He is believed to be around seventy years old and is worth several hundred billion yen, a status he refers to as being a "king," maintaining that the poor can never overthrow him because their own desire for money paradoxically strengthens his position. His philosophy holds that poverty is an inescapable trap, as the yearning of the impoverished to escape their station ultimately reinforces the power of the existing wealthy elite.

In terms of personality, Hyoudou is depicted as exceedingly depraved, sadistic, and classist, frequently referring to those less fortunate as "scum." He looks down on the lower class and has virtually no sympathy for their predicaments, believing they have no one to blame but themselves. He delights in bizarre and disturbing stunts, often at the expense of his own employees, whom he forces to participate in humiliating acts such as drinking wine from a bowl he has put his feet in. His moods are erratic; while he can occasionally be in an uncharacteristically good or even kind mood, this state can be shattered by something as tiny as a pebble. He is also a widower, having lost his wife Sophie prior to the events of the series.

Hyoudou's role in the story is that of a sinister puppet master and Kaiji Itou's true nemesis. He first appears observing the conclusion of the Restricted Rock-Paper-Scissors game on the ship Espoir, commenting on Kaiji's unique survival abilities. After Kaiji survives the Steel Frame Crossing gamble, Hyoudou personally invites him to play a game of E-Card against his subordinate, Yukio Tonegawa. Following Kaiji's victory, Hyoudou shows his cruel nature by forcing Tonegawa to kneel in apology on a smoldering hot iron plate for ten seconds as punishment for his failure. Horrified by this act, Kaiji identifies Hyoudou as his true enemy and challenges him directly. This leads to the Tissue Box Raffle gamble, where Hyoudou demonstrates his own cunning. He outsmarts Kaiji by detecting his attempt at foul play, folding the winning lottery ticket so he could identify it by feel, and wins the gamble. The result is that Kaiji loses four fingers on his left hand and all of his winnings. Hyoudou later appears monitoring Kaiji's challenge against a pachinko machine called The Bog, threatening the casino owner, Seiya Ichijou, with a lifetime of forced labor in an underground camp if Kaiji wins.

Key relationships define much of Hyoudou's cruelty. He is a terrible father to his two sons, Kazuki and Kazuya Hyoudou. He shows clear favoritism toward his eldest son, Kazuki, while frequently neglecting his youngest son, Kazuya. He reprimands both for things beyond their control, contributing to Kazuya's deep-seated psychological issues. His relationship with his right-hand man, Yukio Tonegawa, is one of master and abused servant, where Tonegawa lives in constant fear of Hyoudou's unreasonable demands and brutal punishments. His relationship with Kaiji Itou is the central conflict of the series; Hyoudou views Kaiji as an intriguing insect whose struggles provide entertainment, while Kaiji comes to see Hyoudou as the embodiment of evil that must be defeated.

The character shows notable development, particularly following the events involving his younger son. After Kaiji defeats Kazuya in a high-stakes gamble called One Poker, Kazuya falls into a coma. Hyoudou becomes furious and grief-stricken, interpreting the mercy shown to his son by Kaiji as a rule violation. He declares Kaiji's win invalid and establishes a manhunt division within Teiai to recover the money and capture the trio. He abandons much of his business operations to maintain a constant, inconsolable vigil by his son's hospital bed, fluctuating between depressive episodes and fits of rage. His frustration over being unable to awaken Kazuya despite his vast resources leads him to even more extreme behavior, demonstrating that his immense power has limits when faced with personal tragedy.

Hyoudou possesses several notable abilities. He is a skilled shyster and gambler with talents for winning, which has earned him the title of "king" by some. He is mentally sharp and experienced in deception, able to instantly detect Kaiji's plan to cheat in the Tissue Box Raffle and subtly impose his own advantageous rules. He wields absolute control over the Teiai Corporation and its employees, who fear him to a monstrous degree. He has also invested significantly in underground bunkers, believing true wealth is the ability to maintain a life of luxury regardless of external circumstances, such as wartime.