"Earl and Fairy" is a manga series set in 19th-century England, blending historical fiction with fantasy elements. The story centers on Lydia Carlton, a young woman with the rare ability to see and communicate with fairies, earning her the title of "fairy doctor." Her life takes a dramatic turn when she encounters Edgar J.C. Ashenbert, a self-proclaimed earl who claims to be the descendant of the Blue Knight Earl, a legendary figure entrusted by the fairy queen to protect her realm. Edgar seeks Lydia's expertise to locate a mystical sword, the Merrow's Sword, which is key to proving his lineage and securing his rightful title.

As Lydia becomes entangled in Edgar's quest, she discovers his past is shrouded in mystery and danger. Edgar was once a captive of a criminal organization known as the Prince, and his escape has left him hunted by its members. Despite his charming demeanor, Edgar's motives are often ambiguous, and Lydia must navigate his manipulative tendencies while uncovering the truth about his identity. The narrative explores themes of trust, loyalty, and the clash between human ambition and the supernatural world.

The story unfolds through a series of adventures as Lydia and Edgar travel across England and Scotland, encountering various fairy creatures and unraveling secrets tied to the Blue Knight Earl's legacy. Supporting characters include Raven, Edgar's loyal servant with a tragic past, and Nico, a fairy cat who serves as Lydia's companion and advisor. The interplay between the human and fairy realms is central to the plot, with Lydia's knowledge of folklore and fairy customs proving invaluable in overcoming obstacles.

The manga balances romance, mystery, and fantasy, with Lydia's pragmatic and compassionate nature contrasting Edgar's cunning and often morally ambiguous actions. Their evolving relationship forms the emotional core of the series, as Lydia's influence gradually softens Edgar's hardened demeanor. The narrative also delves into the consequences of human greed and the exploitation of fairy magic, highlighting the delicate balance between the two worlds. Through its intricate plot and well-developed characters, "Earl and Fairy" offers a compelling exploration of love, identity, and the enduring allure of the supernatural.