One day, a tower appeared in the skies of all the major cities… Humans were suddenly summoned to become “Walkers”, and they needed to clear the tower to save the world. . . “Floor 77” The “Stone of regression” was discovered. Walkers could now “return” to the past. Slowly… everyone left. . . Humanity’s last hope, “Carpe Diem” was formed, joined by people who refused to abandon the world. . . The last Walker reached floor 100. He no longer knew what to believe.