Well, a 'to be read backwards short story' could be an experimental form of storytelling. It might play with the normal flow of a story. For example, the events that would usually build up to a climax are presented in reverse, so you start with the resolution and work your way back to the beginning, which can make the reader think about cause and effect in a whole new way.
To write a 'to be read backwards short story', first think of the end of the story. Then, create events that would lead to that end in reverse order. For example, if the end is a character finding a lost treasure, start with that and then write about how they got to the point where they lost it in the first place.
Writing a short story backwards can be challenging but interesting. You need to first decide on the final outcome and then figure out the steps that led to it. Focus on creating a logical and engaging reverse narrative.
Manga is read backwards because that's the traditional way it's been formatted in Japanese culture. The layout and reading direction are part of the unique style.
The reason manga is read backwards is related to the way Japanese language and writing systems are structured. Also, it's been a convention in the manga industry for a long time. So, that's just how it's done.