The story takes place in the fictional city of Orario to when gods all came down seeking excitement, limiting their divine powers to perceive and experience the hardships that thrives on the lower world. Offering mortals to fight monsters assorted in an underground labyrinth known as Dungeon (ダンジョン, Danjon). Adventurers visit the dungeon to defeat monsters and take their crystal shards, which are used to craft magic items, among other treasures; however, they can also be exchanged for the world's currency. The people of Orario join groups called Familia (ファミリア, Famiria), who serve a range of functions from dungeon crawling to crafting items. Each Familia is named after and serves a resident deity. In a fashion similar to role playing games, the adventurers are grouped into levels, increasing their levels and abilities according to their achievements.
The story follows the exploits of Bell Cranel, a solo adventurer under the goddess Hestia. As the only member of the Hestia Familia, he works hard every day in the dungeon to make ends meet while seeking to improve himself. He looks up to Ais Wallenstein, a famous and powerful swordswoman who once saved his life, and with whom he fell in love. He is unaware that several other girls, deities and mortals alike, also develop affections towards him; most notably Hestia herself, as he also gains allies and improves himself with each new challenge he faces.