Ilusia begins his existence as a reincarnated human trapped within a dragon egg, navigating a perilous fantasy world with only fractured memories of his former life as a Japanese man. Driven by survival and a desire to evolve into increasingly powerful forms, he seeks human connection despite the fear his monstrous visage provokes. Myria, a young mage who names him after the Illusia flower—symbolizing courage and resilience—becomes his first ally, though their bond fractures under the risks posed by his transformations.

His evolutionary journey unfolds through distinct stages: a vulnerable Baby Dragon with yellow scales and minimal combat skills matures into a Young Plague Dragon, marked by dark gray-purple armor, venomous Disease Breath, and Dragon Scale Powder. Later forms—Ouroboros, Oneiros, and Apocalypse—introduce dual-headed physiology, illusion-based powers via six eyes, and apocalyptic destruction, respectively. Humanization skills grant him a humanoid guise with pale skin, white hair, and residual draconic traits, reflecting his yearning for acceptance.

Timid yet principled, Ilusia balances naivety with decisive action, prioritizing others’ safety even when misunderstood. He manipulates his own toxicity to repel allies like Myria for their protection and resists the Divine Voice’s coercive guidance toward destructive evolution. Relationships anchor his moral compass: Partner, his Ouroboros-stage counterpart, dies defeating a shared foe; transient allies like the Black Lizard, dragon hunter Volk, and Treant aid his survival until fate separates them. Unintentionally leading the Giant Orangurang’s pack after defeating it, he shoulders leadership reluctantly, his influence expanding alongside his power.

Survival in hostile environments and overcoming distrust define his early trials, while later conflicts pit him against entities like Saint Lilyxila and Dragon King Diabolos, unveiling his lineage as the "Dragon King’s Son." Titles like "Ryuo" and "World’s Strongest Proof" cement his apex status, burdening him with mediating human-mythic tensions. Abilities evolve from basic Roll and Scorching Breath to Healing Hands, Razor Wind, and reality-warping illusions. Each skill mirrors his struggle to reconcile draconic instincts with human empathy, a duality echoing in his persistent efforts to bridge societal divides through communication, even as prejudice challenges his resolve.