Jun Kagami emerges as a central antagonist defined by physical fragility, offset by his alliance with Ouroboros, a serpentine Mecha-Ude that augments his strength. Viewing Mecha-Ude as mere instruments, he clashes with Ouroboros’ unwavering loyalty. Their synchronization transforms his white hair to vibrant green, fading to pale when strained. Ouroboros wields the power to sever bonds between other Mecha-Ude and hosts, a capability magnified upon evolving into Asclepius.

As the Kagami Group heir’s spurned younger brother, Jun’s destiny unravels when Alma—the rare Trigger Arm Mecha-Ude meant for him—chooses Hikaru Amatsuga instead. Consumed by resentment, he infiltrates Hikaru’s school, masquerading as frail to manipulate peers while orchestrating Alma’s retrieval. His strategy hinges on psychological warfare, relentlessly mocking Hikaru’s perceived weaknesses to destabilize his resolve.

Jun’s autonomy shatters when Fist, a manipulative Mecha-Ude puppeteering both the Kagami Group and ARMS, discards its host to seize control of Jun’s body, dyeing his hair azure as a mark of subjugation. Yet later, he surfaces alongside Hikaru and Aki, opposing a mutual threat. Ouroboros persists in addressing him as “Master Kagami,” their bond lingering ambiguously despite Fist’s corruption.

A chronic illness and sharp intellect, exploited by his family for experimental ends, underpin Jun’s trajectory. Once a cunning strategist, his agency erodes under external forces, muddying his moral stance. His story closes without resolution, poised between the shadows of past ruthlessness and faint glimmers of potential change.