Here's another panel discussion topic from
AnimeIowa programming:
There are only six ways to get to an isekai.
Each way has different implications for the
plot and characters. Let’s explore!
For those not familiar with anime, isekai is basically portal fantasy. The character starts in a fictional version of the Primary World and is transported to another one.
Although I haven't been able to find a definitive list of the six ways referred to in the panel description, I have seen mentions of several: being summoned by a god or other supernatural being, opening a door or other gateway and walking through, and the ever-popular reincarnation, often as the result of being run over by a truck while hurrying to school (which led to the meme of Truck-kun, a special truck that goes around running over people and sending them to other worlds).
Obviously being called to the other world by a supernatural being is going to have your character starting out right away with a reason to be there, and very likely a Quest that must be accomplished -- and a greater chance of being able to go home when it's all over, since presumably your supernatural patron can send you back.
Opening a door is probably the most voluntary one -- and the one that's most likely to have your character's subsequent problems being seen as the result of excessive curiosity. If he'd just refrained from poking his nose where it didn't belong, he wouldn't be in this pickle.
Reincarnation is probably the one that is the biggest sticking point with Moral Guardians in Western countries, because the concept of reincarnation comes from the dharmic faiths, and is a concept that Christianity specifically rejects (as does Islam, although majority-Muslim countries probably have other objections to anime that would be raised before theological issues about what happens after death). Russia has specifically banned isekai anime on the grounds that portraying death and reincarnation as a gateway to a brighter and more exciting world is encouraging self-destructive behavior in young people discontented with their lives in the here and now, and it's quite possible that theological disapproval on the part of the Russian Orthodox Church played a part in the government's willingness to pass the ban, even if they phrased their reasoning in primarily secular terms.
From a purely narratological perspective, isekai initiated via reincarnation are interesting because the character often has to have an inciting incident to remember his or her previous life, and thus to begin the quest. For instance, in My Next Life as a Villainess: All Roads Lead to Doom, the protagonist is hit on the head at the age of eight and suddenly remembers her previous life as a Japanese schoolgirl obsessed with an otome game called Fortune Lover, and realizes she's now living in that world, and has a limited amount of time to avoid a whole range of horrible outcomes if the game's protagonist bests her. That ticking clock is the big driver of the plot of the first several manga, and
By contrast, most of the other paths into an isekai world leaves the protagonist well aware of the life he or she has left behind. Depending on what the protagonist left behind, that may increase the tension, whether from desire to get back home, or desire to not be sent back after the quest has been completed.