Dio was created as a genetic counterpart to Casshern, meant to procreate with Leda and ensure the continuation of robotic life. However, like Casshern, his original purpose was discarded, and he was instead trained into a warrior for Braiking Boss’ empire. Though Dio and Casshern were equals in design, Casshern was always stronger, faster, and more successful, leaving Dio to live in his rival’s shadow. This imbalance between them created a festering envy within Dio, who spent his entire existence chasing after Casshern, desperate to surpass him.

After Casshern killed Luna and caused the Ruin, Dio abandoned Braiking Boss, setting out with Leda in search of a way to reclaim power. Leda, ambitious and manipulative, convinced Dio to raise an army, claiming that they could rule the ruined world together. However, Dio cared little for ruling his only focus was revenge. As the world crumbled, his hatred of Casshern only deepened, leading him on a path of destruction in pursuit of their inevitable final battle.

Dio is physically identical to Casshern, but his sharp, angular features and cold, calculating eyes distinguish him from his rival. He has a lean, battle-hardened physique, built for speed and power, and wears a dark variation of Casshern’s bodysuit, further emphasizing his role as his counterpart and rival.

Unlike Casshern, whose expressions are often melancholic and reflective, Dio’s face is hardened by anger and pride, his intense gaze reflecting his relentless desire to win. Throughout the series, his movements and posture are rigid and controlled, embodying a fighter who refuses to yield until his mission is complete.

Dio is driven, prideful, and consumed by rivalry, dedicating his existence to surpassing Casshern. Unlike Casshern, who searches for meaning in a dying world, Dio’s purpose is singular and unwavering he exists only to fight, to prove himself, and to finally overcome the one opponent he could never defeat.

Although he is cold and ruthless, Dio is not without emotion. His hatred for Casshern is deeply personal, fueled not just by jealousy but by a desire to define his own existence. He refuses to accept a life where he is second place, seeing his final battle with Casshern as the only thing that truly matters. While Leda seeks immortality and power, Dio rejects the idea of ruling the world, knowing that only in combat, only in the thrill of surpassing Casshern, can he find fulfillment.

By the time of his final battle, Dio experiences true passion, something that ruling the world or eternal life could never give him. In the moment of his long-awaited victory, he finally feels complete, choosing to let go of everything else and embrace the Ruin, having achieved the only thing he ever wanted.

• A Rival in the Shadows
  From the beginning, Dio is Casshern’s shadow, his constant rival and counterpart. While Casshern wanders in search of redemption, Dio hunts him for revenge, following a path of rage and destruction. Unlike Casshern, who has forgotten his past, Dio remembers everything, holding onto his hatred with unwavering determination.

• Manipulated by Leda
  Although Dio is driven by personal ambition, he initially falls under Leda’s influence, helping her gather an army to reclaim power. However, he is never truly invested in ruling the world, and eventually, he sees through Leda’s manipulations, choosing to cast her aside and fully commit to his final battle with Casshern.

• The Final Battle with Casshern
  Dio’s entire existence leads up to his final battle with Casshern, where he fights with everything he has, fueled by a lifetime of frustration and determination. In this moment, Dio feels alive in a way that he never has before, experiencing true passion and purpose. When he finally defeats Casshern, he realizes that his journey is complete he has achieved what he was created for, and with no regrets left, he chooses to let the Ruin take him, content in his final moments.