I Built A City At Doomsday

He was fighting in a post-apocalyptic world one second, and the next, he was back in time before it even began!?
He experienced immense suffering over those nine years, to the point of eating earthworms every day and almost losing everything. Reminiscing his past, he vowed to safeguard everything he held dear this time.
Suddenly, a mysterious ray of light entered his body, which would evolve into his most vital asset in the coming apocalypse!
He was unaware at the time that it was more than just a place for him to farm or store stuff; it was so miraculous that it could support him and even a vast civilization!
He thought he was prepared for everything because he evolved ahead of time and made preparations. But who would have thought his rebirth itself had altered the course of his previous life's history?
A thrilling and daring mission to ensure survival at doomsday had begun!