Thank you for enlightening me on the history of isekai like stories.?
But I don't think the myths involving Sisyphus and the others with similar stories in Greek mythology qualify as a sort of isekai story because their souls didn't reincarnate into another world, but instead they were resurrected and returned to the land of the living.
From the Wikipedia for Isekai: The genre can be divided into two types "transition into another world" (異世界転移,
isekai ten'i) and "reincarnation into another world" (異世界転生,
isekai tensei).
[2] In "transition into another world" stories, the protagonist gets transported to another world (E.g by traveling into it, or being summoned into it).
[2] In "reincarnation into another world" stories, the protagonist is sent into another world after dying in the real world. A common method of death is being run over by a truck and dying, spawning the meme of "
Truck-kun", a truck which appears in many isekai series that kills the protagonist and the protagonist reincarnates into a different world.
Hades was considered the Underworld and to get to it, you had to die, get transported by a god/goddess or go through a portal to it.
From the Wikipedia for Hades: "Hades and his two brothers, Poseidon and Zeus, drew lots
[18] for realms to rule. Zeus received the sky, Poseidon received the seas, and Hades received the underworld,
[19] the unseen realm to which the souls of the dead go
upon leaving the world as well as any and all things beneath the earth."
(All Bolding added by me).
Hades was not considered "hell" like the Christian mythos does, it was considered another world you passed on to. The living could visit it and live there even; such as Leuce a lover of Hades who even died of old age there. Just do not eat the food. Heroes seemed to have had a revolving door sort of requirement to visit there and get their Heroic passport punched from the number of them going there alive or dead.
I was just giving you older than 20th century examples, since you asked for an Isekai getting transported (by dying) before modern Isekai stories were written. Technically the first type of Isekai, means you could fly to it by spaceship even, which really opens up this can of worms. If you did not add the must have died bit to your Isekai requirement then the list would have been much, much longer. Heck I stayed away from Chinese and Japanese mythos; seems everyone was taking the highway to another world and back in some of their stories, dying first or not.
Good luck on your search though
