There are and have been so many stories of that type being released, especially in the light novel or manga section, and I noticed that these stories often follow a similar pattern and have a similar setting:
- the "other world" mostly has a medieval setting and is often constructed as an RPG with a leveling system.
- That world normally contains different fictional species (humans, elves, demons etc.) who are usually capable of using magic.
If the protagonist isn't born into that fictional world he's either being transported there or reincarnated. And these two ways also mostly follow a similar pattern, aside from the fact that the original world is Japan in the 21st century:
- if he's being reincarnated he'd usually died in his original world, normally due to an accident with a truck.
- If he's being transported there it's often due to a summoning by a royal family. They want the summoned "heroes" (it's often not only the protagonist who's been summoned) to help them to defeat the demon king who's invading the country or at least is a threat to the people. If the protagonist wasn't summoned by anyone he often becomes an adventurer.
Where did those "clichés" come from and what makes these types of stories so popular?