Once a loyal court magician for the Crown Prince, Alec Ygret dedicated himself entirely to support magic, enhancing his allies and keeping them safe in battle. His reward is to be called incompetent and cast out of the royal party. The situation worsens when the prince has him banished from the entire royal palace, leaving Alec at his lowest point and stripped of his position.

The story is set in the Galdana Kingdom, a world where magic is integrated into daily life and adventurers explore dangerous dungeons. Alec is a genius magician who, as a commoner, was restricted to using only support magic while serving the nobility. Unbeknownst to the prince, Alec was trained in other powerful disciplines, but he chose to fulfill his supportive role to protect his teammates.

Hitting rock bottom, Alec reunites with Yorha Eisentz, an old friend from his magic academy days and a former member of the legendary party known as Lasting Period. Yorha invites him to rejoin the team that once made history. Together with their former comrades, including Krasia Annerose and Ornest Rain, Alec revives Lasting Period and returns to dungeon exploration, beginning a new chapter in his life.

As Alec and his party conquer dungeon floors, the narrative contrasts his success with the Crown Prince's struggles, as the prince's party quickly discovers how weak they are without Alec's essential support magic. The story also reveals that the prince had previously ordered Alec not to use flashy spells that would outshine the royalty, which forced him to focus solely on support magic in the first place.

Notable narrative arcs include the revival of Lasting Period, battles against floor bosses in the royal dungeon, and encounters with the Shadow Guild, a shadowy organization experimenting with humans and seeking Yorha for her abilities as a pureblooded Seeker. The story also explores the history of the Ten Strongest who once sealed an evil goddess, as well as the backgrounds of each party member, including Ornest's quest for strength and Krasia's complicated family history. The series builds toward confrontations with powerful adversaries known as Title Bearers and the revelation of a larger conspiracy threatening the kingdom.