20代に「十二国記って異世界転生、転移の原点なんでしょ？」と言われ、反射的に「新井素子『扉を開けて』とかもっと前からあるよ」と言ったけど、他にもあるよね - Togetter

This page discusses the origins of isekai (alternate world) transmigration and reincarnation stories. A poster mentioned that when a 20-something claimed 'Twelve Kingdoms' was the original, they countered with Motoko Arai's 'Opening the Door,' which predates it. Comments reveal various earlier works: 'The Twelve Kingdoms of Narnia,' 'Saint Seiya Dunbine,' and 'The Mark of the Royal Family.' For children's literature, works from the 1980s are cited. The discussion highlights how the genre classification of 'isekai' is relatively recent, despite similar stories existing much earlier across different media.