Poseidon emerges as the central antagonist, commanding the seas as patriarch of the Poseidon Family. Driven by envy of the Triton Family’s thriving dominion in Atlantis, he masterminds their extermination 5,000 years before the story’s events, slaughtering all but Triton—the lone survivor he hunts across millennia to erase the last trace of his rivals.

A methodical and merciless strategist, Poseidon wields cataclysmic force to secure his supremacy, unleashing tsunamis to drown coastal civilizations and engineering schemes to pin Tokyo’s devastation on Triton. His cruelty escalates with biological manipulation, spawning a monstrous heir by grafting a sponge into the form of Triton’s trusted companion, Pipiko. The abomination’s chaotic fury compels a fragile alliance with Triton, which Poseidon shatters by orchestrating new calamities to implicate his foe.

He rules his aquatic realm and 33 progeny with an iron grip, though Triton dismantles his lineage by defeating each heir. Poseidon weaponizes deceit, forging proof of Triton’s “atrocities” to rally humanity against him. His hubris proves fatal: during a climactic battle in his submerged fortress, Triton and the elder turtle Ganomosu trigger a cataclysmic explosion that consumes the stronghold and seemingly claims Poseidon’s life.

The deity personifies tyrannical rule and the ruin spawned by unchecked ambition, standing in stark contrast to Triton’s relentless pursuit of justice. His enduring legacy lingers in ecological upheaval and societal fractures, echoing the clash between oppressive dominion and defiant resilience.