Hiroki Moriyama, a member of Ryuzu Myoujin’s antagonistic Company, harbors a warped worldview forged by childhood bullying. These formative experiences drove him to equate violence with justice, enforcing rigid rules through intimidation as his peers’ fearful compliance reinforced his methods. Convinced of his heroism, he viewed Company as defenders against perceived evils like Chrono Shindou and allies, though his hypocrisy and arrogance frequently clashed with his self-righteous claims.

Serving under Ryuzu, he demonstrated tactical skill by deploying electric barriers and robotic units to shield allies and stall opponents. His unwavering loyalty extended to witnessing Ryuzu’s revival via cloning, cementing his place in the group’s hierarchy. At the United Sanctuary Branch, he confronted Taiyou Asukawa in a cardfight, deriding his opponent’s fragility while touting his own ideals. Victory via Quadruple Drive allowed the branch’s destruction through Am Chouno’s Zodiac Time Beast, after which he coldly discarded Am, underscoring his merciless persona.

Following Company’s collapse, Hiroki enrolled in Taiyou’s school, shedding his obsessive pursuit of "justice" for a calmer, empathetic demeanor. He consoled Taiyou during emotional turmoil, recognized his rival’s tactical growth, and aided him against threats like Valeos. While embracing this maturity, he retained his tenacity and confidence, balancing growth with enduring traits.

His trajectory spans trauma-driven villainy to redemption: strategizing for Ryuzu, clashing with protagonists, and ultimately reconciling through self-reflection. This arc mirrors themes of rigid ideology yielding to change, framing him as a complex, evolving figure within the narrative.