Short answers, pulled from the story.
Isekai is a Japanese word meaning "another world." It names a genre of fiction in which a person is transported from ordinary life to a different world, often gaining powers or importance they lacked before. The Oxford English Dictionary added the word isekai in March 2024.
Warrior from Another World, published in 1979 by Haruka Takachiho, is considered the first modern Japanese isekai story. The first Japanese isekai anime is Aura Battler Dunbine, which aired in 1983.
The anime adaptation of Sword Art Online, released in 2012, is widely credited with sparking the modern isekai boom and with popularizing the term isekai itself. Its creator disputes the isekai classification, but the series is widely seen as a turning point for the genre's mainstream popularity.
J-Novel Club CEO Samuel Pinarsky explained that the novel-posting website Shosetsuka ni Naro lists chapters by title only, with no separate summary. Writers responded by making their titles long and descriptive enough to serve as their own pitch to potential readers.
A 2024 survey of isekai viewers in English-speaking territories found the average age to be about 30, with 65 percent being male. Kadokawa editor Satoshi Arima identified salarymen wanting to switch jobs as a core audience, drawn by the fantasy of living life on their own terms.
Reverse isekai is a subgenre in which a being from a fantasy or futuristic world is transported to present-day Earth and must adjust to ordinary life. Mitsuteru Yokoyama's Sally the Witch (1966) is cited as an early example, making the subgenre older than mainstream isekai.