[Participant in the April 2024 Royal Road Writathon challenge]

Earth is Lost.

Driven to the brink of extinction and forced to abandon the surface to the impossibly powerful Kaiju that claimed it. Humanity survives only by delving deep into the Earth's mantle in Subterranean Arks. Doomed to a slow withering end.

Raymond Ryker isn't a hero. When humanity created their own giant mechanized combat units to fight against the monsters at their door, he was merely one of thousands to step up and fight for the cause. But the best surviving pilot humanity has ever known doesn't fight for glory or honor. Not even to save the lives he's sworn his life to protect. He fights to kill the monsters that took everything from him. To Raymond, every Kaiju he kills is merely one more step towards avenging the countless lives lost, cities destroyed, and the world that was taken from him.

When the genius Doctor Beck Wallenstein, creator of the Archangel program and countless other advances in the fight against Kaiju, concocts a mad plan to send a human consciousness back in time to inhabit the body of their younger self. There is no choice but to take the mad gamble, and Ryker immediately volunteers for the program.

But the experiment goes wrong during a critical phase and rather than inhabit the body of his younger teenage self like he should have. Ryker's mind is transplanted into the body of a newly hatched Kaiju. Trapped in the body of a monster and unable to warn humanity about the cataclysm to come. Ryker takes the burden of saving the world onto his shoulders. He'll use everything he's ever learned about the enemies he despises to forge his new body into a weapon to surpass all others. He'll grow stronger, faster, and evolve every portion of his kaiju DNA to achieve his goal.

The circumstances have changed but the mission remains the same.

KILL ALL KAIJU!