The story opens against a bleak historical backdrop, with a storyteller laying out the era and establishing the four great tragedies one by one.
The main world is closely linked with the successive worlds. Under immense mental strain, the protagonist accidentally falls into one of these successive worlds.
There, they discover many rules, traveling back and forth between the main world and the successive worlds.
In the main world, they solve one strange case after another and uncover the rules of the successive worlds.
