Warau Yakan is a Japanese creator credited as the original author behind the dark fantasy franchise How to Build a Dungeon: Book of the Demon King. The original work began as a light novel series, for which Yakan Warau is the writer. The franchise was later adapted into a manga series illustrated by artist Toshimasa Komiya, with Yakan Warau retaining the author credit for the story.

The series is published in English by Seven Seas Entertainment, with the first volume released in October 2016. The manga is published under the Ghost Ship imprint, which focuses on mature-themed titles. The work is explicitly intended for mature readers due to its content.

How to Build a Dungeon: Book of the Demon King is Yakan Warau’s most recognized work. The narrative follows a protagonist named Aur who, at the end of his life, successfully becomes a Demon King and begins constructing a dungeon, populating it with fantastical creatures including a succubus named Lilu. The series blends themes of ambition, power, and dark fantasy with explicit mature content. The original Japanese publication was handled by Kill Time Communication starting in 2015, before being licensed for English release.