Haruka Alford, a scientist spearheading a 1999 UN energy initiative on Sansara Island, unwittingly ruptured the boundary between dimensions during a failed experiment, unleashing long-dormant biomechanical horrors. Three years later, his former colleague Takuya Goroza receives a cryptic summons urging a return to the island, only to find Haruka plagued by paranoia, barricaded within the lab, and disavowing the letter’s existence.

Takuya uncovers Haruka’s clandestine work on a dimensional transfer cannon designed to bridge realities. The device’s corruption by the demonic entity Ika Oni triggered an irreversible fusion, binding Haruka’s psyche to the mechanized abomination. Consumed by its influence, he unleashes carnage across the facility, slaughtering personnel—including Lyse, a military liaison—before seizing control of the hybrid monstrosity.

In the climactic duel, Haruka commands the corrupted entity against Takuya piloting the armored beast Hagane. Their clash triggers the island’s collapse, ending with Haruka’s hybrid form disintegrating amidst the cataclysm. Sansara sinks into the ocean, leaving Takuya alone amidst the wreckage as the sole witness to Haruka’s descent and demise.