One Piece: My Crew is from Other World - Chapter 530: Special Mission: God’s Body

THE LAST MARINE– Series SynopsisThe world ends not with a bang, but with a prayer and a shattered test tube. Marine Quinn Calloway, a man accustomed to the structured chaos of war, finds himself on leave in the deceptively peaceful mid-sized city of New Havenburg when the unthinkable happens. Dr. Lucian Kael, a brilliant and devoutly religious scientist at the prestigious Blackwood Research Institute, driven by a fervent desire to unlock humanity's “divine potential,” makes a catastrophic miscalculation. His experimental “Kael Strain” virus, designed for benign purposes, is accidentally unleashed, and its effects are swift, brutal, and biblical in their apocalyptic scope.

Three Days of Happiness is a novel by Sugaru Miaki, also known as Fafoo. It’s a rewritten version of the story originally posted to 2ch.

The premise of the story revolves around a shop where one can sell away the remaining years of their life, and the consequences of doing so.

“I Say A Little Prayer” is a short related story which was posted along with the novel’s release. It spoils some things about the main story, but nothing major.

The world was never the same after that day.Humanity learned that they weren't alone in the universe, but that wasn't something they had the time to worry about.Their realization was accompanied by catastrophe.Creatures beyond their wildest imaginations poured down from the sky and appeared from the earth. They slaughtered humans as if it was their singular purpose, driving them to the brink of extinction.The people of the world did everything in their power, developing unique traits and technologies to create a united front their enemies couldn't penetrate.They secured victories and repopulated, feeling as if they stood a chance against the foreign invaders.They fought and they fought, doing everything they possibly could to ensure their survival.Until the Great Calamities appeared.In front of them, humanity was nothing regardless of its efforts.One by one, the worlds were turned into piles of rubble in between the cracks of their teeth. Civilization was torn apart, and the evolved humans living within could do nothing to stop its collapse.Humanity itself was left extinct, and in the end, only a single man was left alive amidst the chaos.Why?For what reason were they punished so?Nobody knew why the attacks began in the first place.He looked into the distance at the memories of the past and firmed his resolve.“It can only be me.”He knew of a miracle that could return him to the place of those memories.He knew of a way to make the wheels of time spin in reverse.And using it, he alone would save humanity from its doomed fate.That was his sacred duty as its final survivor.

This is a world where humans, demons and mysterious beasts coexist.

Humans cultivate mysterious qi. Demons cultivate corporeal bodies. Mysterious beasts cultivate soul perception.

A legend says that in the middle of an endless rainforest, there are extremely powerful existences; they are called demon kings.

Some demon kings have a tyrannical corporeal body, some are experts in illusions.
Some demon kings are proficient in magic, some can even move mountains.
Some demon kings are able to sense things thousands of miles away.

These demon kings rarely appear in the human world. Even if they emerge in the human world, they would reincarnate in human form; assimilating with mankind while seeking to breakthrough realms…

- Description from Novelupdates