The story takes place in the distant future when humankind has declined. Disasters and wars have destroyed the old prosperous civilization, and the land has been devastated by plant extinction and ecological collapse. In the last city of humankind —— Havenswell, the remaining people, gathered by the legend of the Elysium, wandered in and out of the city walls, struggling to survive. Simultaneously, a black slurry called Mud emerged from underground and soon spread to all corners of the city, eating away at people's living space.
In the face of forces beyond imagination, the human beings resented their weakness but were powerless to fight back. They were living in the cracks of the city, waiting for destruction. In a desperate situation, a group of seekers called Bladers appeared in Havenswell, bringing a slight change in the current situation. The 'Blader' had the appearance of humans but were brand new creatures created with unknown technology. With their missions in mind, they embarked on a lonely and dangerous journey.
