Trapped within the vessel of one young Yuji Itadori, his soul doesn't have many places to go. When he's not inhabiting the body of the teen, there is only his innate domain and, well, that can get rather boring. Especially at night. At least during the day, he can watch the world through Yuji's eyes.

So maybe that's how he found himself in this realm. A place between sleep and awake, life and death, where only lost souls wind up.

The realm is oddly peaceful and never-ending. A never-ending night full of glimmering stars shines above a forest of trees taller than life.

After a while of wandering, he finds himself at a clearing. The sound of running water pulls his attention to the waterfall that leads into a pool of water so clear it looks like glass.

But that's not the most interesting thing he finds there. No. What he finds...is another lost soul.