In a world where a person's destiny is decided by the Skill Fruits they consume, eating a second fruit is a death sentence. This is the harsh reality facing Light Underwood, a young man who dreams of becoming a great adventurer alongside his childhood friend, Lena Floria. While Lena obtains the legendary Sword Saint skill and is celebrated as a prodigy, Light receives the seemingly useless Fruit Master ability, which only allows him to farm and cultivate nuts. His dreams shattered, Light resigns himself to a quiet life as a farmer in a remote village, where he takes in a kind orphan girl named Ayla.

One day, Ayla accidentally cooks several Skill Fruits into their stew. Light eats the meal, fully expecting to die, but instead of perishing, he survives and gains a second skill. He discovers the hidden, true power of the Fruit Master: it grants its wielder the ability to consume an unlimited number of Skill Fruits without dying, allowing them to acquire countless abilities. This revelation rekindles his dream of becoming an adventurer.

Light travels to the Holy City to register at the Adventurer's Guild, where he reunites with Lena. Despite her high rank, Lena is miserable, trapped in a political and abusive party arranged by the corrupt Inspection Officer known only as the Saint. Light rescues Lena, and together with Ayla, who possesses the Appraisal skill, they form the party Luxeria. Their group consists of Light, who slowly builds a diverse arsenal of skills; Lena, the party's powerful swordswoman; and Ayla, who provides crucial intelligence by identifying enemies' abilities.

As Luxeria takes on various quests, they uncover dark secrets about the guild. The Saint wields immense authority and secretly commands an elite squad called Black Swan to operate in the shadows, eliminating threats and exploiting powerful adventurers for her own purposes. The party investigates a manor where adventurers have gone missing, battling a Necromancy user named Dratena, and confronts the existence of dangerous taboo skills. They also encounter allies like Monica Bolst, a legendary blacksmith who crafts a powerful sword for Light. Throughout these adventures, Light is forced to carefully manage his growing power, often hesitating to eat new fruits in dangerous situations instead of becoming instantly invincible.

The narrative explores two intertwining paths. While Light and Ayla undertake missions to grow stronger and challenge the guild's corruption, Lena undergoes her own development, proving she can stand as a hero in her own right. In one significant arc, Lena teams up with a former antagonist to protect a town from waves of frenzied monsters, showcasing her leadership and combat prowess. The Saint views Light as a threat to her control and seeks to capture him alive to exploit his unique ability, setting her up as the primary antagonist. As Light continues to defy the rules of his world by consuming more Skill Fruits, he and his companions journey to defeat the plotting Saint and uncover the truth behind a mysterious girl who appears, vowing revenge.