Ten years ago.
The present world.
A young man was walking along the street in a university campus.
He lived a leisurely life just as he had for over twenty years in this utterly peaceful world.
Just when he thought that the days ahead would be as stable, harmonious, and tranquil as they had been for the past hundred years.
As he walked along the street, he suddenly clutched his head, his body uncontrollably trembling, sweat unconsciously covering his back.
In the young man's mind, images of his own brutal death kept emerging.
Wave after wave of intense pain and fear continuously tormented his soul.
After a long while, the young man, recovering from those negative emotions, realized the peculiar situation he was facing.
"Have I returned to ten years ago?"
"How is that possible?"
"How could this happen?"
