Alternate universes are a tried and true trope for writers to fall back on when they want to explore different aspects of their characters. There are many, many examples of alternate universes throughout the history of fiction and the trope reaches all the way back to some of the earliest examples of the written word. It makes sense as these differences allow writers to explore their characters in new and interesting contexts. Marvel loved its "What Ifs," DC Comics had its "Elseworlds" tales, and anime has its own ways of enjoying the freedom that alternate universes can give.
Source：https://www.cbr.com/bungo-stray-dogs-beast-important-reading/
