Maou no Hajimekata

Maou no Hajimekata (魔王の始め方), officially subtitled as How to Book on the Devil, also known as How to Build a Dungeon: Book of the Demon King in English, is a multi-stream series written by Warau Yakan. The web novel has completed its run, and is the original work. The light novel is currently being published. The manga comic is currently being published. The English release is licensed by Seven Seas Entertainment.

Plot
"I do not trust humans. They’ll betray you without fail.” Aur, the man who had obtained the ability and right to become the Maou at the end of his life of research. Summoning the succubus Lilu, he then sets out on creating his own domain, a gigantic labyrinthine dungeon… The misanthropic Maou taking on the world, the curtain rises on a dark harem fantasy!

Official

 * Official Light Novel Site
 * Official Manga Site