"Fena: Pirate Princess" is a 12-episode anime series set in a fictionalized version of the 18th century, blending historical elements with adventure and mystery. The story centers on Fena Houtman, a young orphan raised in a brothel on an island under British control. After escaping her confined life, Fena reunites with a group of former samurai, the Yukimaru crew, who once served her father. Together, they embark on a quest to uncover the secrets of a legendary treasure tied to Fena's past and a mysterious place called "Eden."

Fena's journey is driven by fragmented memories of her childhood and a cryptic phrase, "Eden," which her father mentioned before his death. The Yukimaru crew, led by the stoic and protective Yukimaru, accompanies her as they navigate treacherous seas, evade rival factions, and decipher clues left behind by her father. Along the way, they encounter the Goblin Knights, a rival group also seeking the treasure, and the British Empire, which has its own vested interest in the secrets of Eden.

The narrative explores themes of identity, loyalty, and the pursuit of freedom, as Fena grapples with her past and her role in the unfolding mystery. The series balances action-packed sequences with moments of character development, particularly focusing on Fena's relationships with the Yukimaru crew and her growing determination to uncover the truth. As the story progresses, the stakes escalate, revealing deeper connections between Fena, her father, and the enigmatic Eden. The series concludes with revelations about the treasure's true nature and its implications for Fena and her companions.

The main characters include Fena Houtman, a spirited and resourceful protagonist; Yukimaru, a skilled swordsman and Fena's childhood friend; and the diverse members of the Yukimaru crew, each with distinct personalities and skills. The antagonists, such as the Goblin Knights and British forces, add layers of conflict and intrigue, driving the narrative forward. The series combines historical aesthetics with fantastical elements, creating a unique setting that enhances the adventure and mystery at its core.