How To Build a Dungeon: Book of the Demon King Vol. 5
Also known as Maou no Hajimekata. Manga by Warau Yakan and Toshimasa Komiya.
"I do not trust humans. They'll betray you without fail." Oulu, the man who had obtained the ability and right to become the Maou at the end of his life of research. Summoning the succubus Lir, 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!