Yuujirou Hanma, bestowed the title "Han Kaiō" (Sea Emperor) by Kaiou Kaku, embodies unparalleled dominance. He is the son of Yuuichirou Hanma and father to both Baki Hanma and Jack Hanma. His background includes extensive, high-fee mercenary and assassination work for governments and organizations. An intimidating aura radiates from him, petrifying those nearby. His personality is defined by extreme violence, arrogance, and a complete rejection of mercy, which he equates with weakness. He harbors deep resentment for perceived weakness and believes pure strength justifies any action. This philosophy extends to his parenting; he subjects Baki to brutal challenges to force his son's development, driven by a desire to create a worthy opponent and mold Baki in his own image. Yet, he displays rare moments of respect, such as sharing a meal with Baki after their battle or expressing affinity for individuals like Doppo Orochi. He also exhibits unexpected sophistication in high-society settings, demonstrating erudition and refined manners. Physically, he possesses a heavily muscled frame, stands 190 cm tall, and has red hair. He treats his body as his ultimate weapon, capable of halting an earthquake with a punch and enduring artillery fire without injury. His fighting style incorporates techniques from various martial arts, though he disdains weapons. Biologically, his inhumanly high testosterone fuels his aggression and underpins his self-perception as the only true "male" specimen, leading to sexually violent acts to assert dominance, such as the rape of Joe Williams. His relationship with Baki is complex and adversarial. He murdered Baki's mother, Emi Akezawa, by rupturing her eardrums and breaking her spine. Despite this, he occasionally demonstrates ambiguous regard for her memory, such as vowing to protect those connected to her. His actions relentlessly push Baki toward greater strength, culminating in a brutal battle where both acknowledge each other's power. Across all media, Yuujirou remains undefeated and is universally recognized as the strongest being. The title "Han Kaiō" formalizes his status as an unconquerable force.