In the city of Orario, beneath an impossibly tall tower, lies the dungeon. Only adventurers who form partnerships with the gods themselves have any hope of defeating the monsters that lie within. But the dungeon is not the only place where monsters exist. Far from Orario, in the ruins of an ancient city, a new threat arises. To counter this threat, the goddess Artemis has come to Orario in search of a champion-but it’s not Ais Wallenstein (the legendary Sword Princess) nor Ottar (the strongest warrior to ever enter the dungeon) that she chooses. Rather it is Bell Cranel, a newbie adventurer partnered with a low-tier goddess.

Shōyō Hinata began playing volleyball after seeing the “small giants” who played the sport when he was in elementary school. He suffers a crushing defeat in his first and last tournament in middle school at the hands of his rival Tobio Kageyama. So, Hinata joins Kurasuno High School’s volleyball team, vowing revenge against Kageyama. However, Kageyama is also on Kurasuno’s team. The former rivals form a legendary combo with Hinata’s mobility and Kageyama’s precision ball-handling. Together, they take on the local tournaments and vow to meet Kurasuno’s fated rival school in the nationals.

The story takes place in a harbor town where a gloomy middle school student named Kai meets a mermaid named Lu.