Dungeon wo Tsukurou

When I woke up, I found myself in the throne room of a palace with a grimoire titled “Let's Build a Dungeon.” The grimoire told me, in my confusion, that I am now the Demon Lord and my mission: "Conquer the world." With help from the grimoire, I built dungeons, defeated the humans, and conquered the world. Now I, the Demon Lord, can finally live a comfortable life of peace, self-sufficiency, and a little gourmet food. But even those modest ambitions are not easy to achieve, as enemies such as demons, sword masters, and knights attack one after another! (Source: Nico Nico Seiga, translated)