The Devil is a Harsh Judge

Kokeru Ken steps off the roof of a skyscraper, ending his waste of life. As he falls, he sees a dark silhouette in the reflection of a window. He hits the ground, surviving the fall. However, he's ended up in a white room, a rusty sword in the centre drawing him in. Where is he? What was that shadow? What's this feeling that he's become part of something much bigger than he can even realize?