Isekai Ittara, Sude ni Imouto ga Maou toshite Kunrin shiteita Hanashi.

I Went to Another World, and My Sister was Already Reigning as the Demon Lord.
異世界行ったら、すでに妹が魔王として君臨していた話。
When I Went to Another World
My Little Sister Was Already Reigning as The Demon Lord

MangaPublishing

ComedyFantasyIsekai

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About this title

Synopsis

When Makoto was summoned to a magical world, he finally found his little sister Misaki, who disappeared two years ago, is now reigning as the Demon Lord of her own kingdom! The bratty Misaki might treat him like a dog, but Makoto knows that the tyrannical Demon Lord is also a lost little girl. (Source: MU)

Publication notes

Isekai Ittara, Sude ni Imouto ga Maou toshite Kunrin shiteita Hanashi. began as a web manga released on the author's Twitter account since 2019, and published in print by Kadokawa since January 27, 2021.