Kurone Kanzaki 
Demon Lord, Retry! (Manga) Volume 5 [EPUB ebook] 

While his trusty advisors work tirelessly to make the Village of Rabbi into a profitable and prosperous hot springs retreat, the Demon Lord dives deep into the Bastille Dungeon in search of something crucial he needs to protect himself in this world — a defense against magic. However, deep in the dungeon, a mysterious force awaits the Demon Lord… Hijinks and comedic misunderstandings ensue as the Demon Lord grows closer to the secret behind this fantasy world.