The story, set two years after the events of "Lost Story," unfolds in Anfiel, the fifth sacred land of the magic nation De La Pena, a location not featured in the previous work. This high fantasy narrative, told in the third person, focuses on Marthe, a fifteen-year-old archaeologist with a single arm, as he investigates a rumored haunted castle. The central mysteries revolve around the castle's existence in a church-dominated nation, the identity of its inhabitant, Eden, and her unique "sentient magic." Marthe's investigation over approximately ten days is intertwined with the suspicious intentions of a man named Feda, who accompanies him to the castle.
Marthe, grandson of the former Pope Zeros Holy, lost his left arm in childhood and now travels De La Pena as an aspiring archaeologist. Eden, the enigmatic mistress of the sole castle in De La Pena, is a mage who commands autonomous magics: Fuwabo, Metsubu, and Vaal. She is portrayed as cheerful with a sharp tongue. Feda, a serious and reserved young man, assists Marthe and travels with him to the castle, though Marthe finds him suspicious. Lililra, Eden's seemingly indifferent but pragmatic attendant, and the "Princess," a woman with Eden's appearance but a different demeanor, are also present. Galferoy Ancient, Guild Master of the Mage Guild "Caldina," warns Marthe about "evil arts," while Auros Elgarden, a renowned mage, makes a guest appearance.
The narrative begins with Marthe and Feda arriving at the castle, a small, structurally simple building that defies the nation's church-governed norms. They are greeted by the "Princess," who reveals the castle's inhabitants are few but that an approaching group of thirty individuals, likely a proxy war between the church and the guild, is expected. Marthe, despite his lack of magical ability and self-doubt, is considered by the Princess and Feda to be surprisingly adept at negotiation. The castle is described as a "sanctuary" built upon sacred ground. As the church's assassins are anticipated, the Princess boasts of her latent power, though Marthe and Feda remain skeptical. Feda then engages Marthe in a philosophical discussion about magic, suggesting that most mages use it without understanding its true nature. He posits that offensive magic's limited elemental types (fire, ice, lightning, wind) stem from humanity's ancient "awe and fear" of natural phenomena, which have become ingrained in magic. This leads to a somber moment as the Princess, her demeanor shifting, apologizes for the predicament, implying a deeper connection to the unfolding events. Marthe and Feda reaffirm their commitment to protecting the castle and its inhabitants, highlighting their shared purpose. Lililra, Eden's attendant, appears, confirming preparations are complete. The Princess declares their resolve to defend their castle, their home, and their friends.
The story then shifts to the role of guilds, particularly the Mage Guild "Caldina" in Anfiel. Guilds serve to regulate professions, contribute to society, and most importantly, provide information. While specialized guilds offer information relevant to their fields, the Mage Guild disseminates knowledge about magic, its history, and related incidents, thereby increasing demand for mages. However, information deemed problematic, such as "evil arts" unrecognized by the Arantes Church, is strictly withheld. Marthe's visit to Caldina seeking information on evil arts is met with polite but firm denials. He is approached by Galferoy Ancient, the Guild Master, who, despite his seemingly ordinary appearance, warns Marthe against pursuing this path, citing the potential for disfavor from both the church and the guild. Galferoy's demeanor, described as almost ecstatic when discussing the topic, and his veiled threat, only solidify Marthe's belief that evil arts exist in Anfiel. Despite the warning, Marthe, driven by his purpose, resolves to continue his investigation, even if it means facing danger. He sets off in his carriage, accompanied by his horse, towards a remote and peculiar location in Anfiel.
Marthe's journey is interrupted by a group of bandits in the mountains. To his surprise, these bandits are mages, clad in mage robes and wielding magical artifacts. They attribute their actions to the "sacred land disparity," a consequence of the war with Echeveria, which has left Anfiel economically depressed. The bandits express resentment towards the ruling powers for neglecting their region. Marthe is then unexpectedly aided by a young man named Feda, who intervenes using a novel form of magic: a massive, bird-like "barrier" that is not destructive but serves as a deterrent. Feda reveals he is heading to a ruined castle, a destination that coincides with Marthe's own objective. He explains his unique magic is a form of "autonomous magic," a field his family has researched for generations.
Upon reaching the ruined castle, Marthe and Feda find it surprisingly small and lacking typical defensive features, leading them to question its purpose. They are confronted by Eden, who claims ownership of the castle and commands three autonomous magics: Fuwabo (fireball), Metsubu (ice shards), and Vaal (lightning whip). Eden's claim of ownership is challenged by Feda, who argues that without proof, ownership reverts to the local authority, the High Bishop. Eden claims to have a deed but has forgotten its location. Feda proposes they stay and search for it, which Eden reluctantly agrees to, albeit with a peculiar "welcome banquet" consisting solely of various jams. The next morning, while investigating the castle, Marthe discovers a hidden compartment beneath the floorboards in Eden's room, containing a diary. The diary entries are fragmented and disturbing, mentioning "you are the 10th person" and "you will die soon," leading Marthe to suspect Eden might be a ghost or something more sinister. He decides to conceal this discovery.
The investigation continues, with Marthe and Feda mapping the castle and noting its unusual lack of defensive structures and its surprisingly clean interior, despite Eden's solitary existence. Feda expresses his belief that the castle might be a site of conflict between the Mage Guild and the Church, a conflict exacerbated by a change in Popes. They discover that Eden's autonomous magics, Fuwabo, Metsubu, and Vaal, are sentient and respond to her commands, a phenomenon that baffles even Feda. Eden's claim of ownership is further complicated when Feda points out that without proof, the castle belongs to the High Bishop. Eden insists a deed exists somewhere within the castle, and Feda agrees to help search for it, proposing they stay at the castle until it's found. Eden, despite her initial resistance to having two men stay, eventually agrees to a compromise: Marthe and Feda will camp outside while she hosts a "welcome banquet" the next morning. The banquet, however, turns out to be an elaborate display of Eden's extensive jam collection, which she considers her sustenance and a form of self-expression. Despite the bizarre welcome, Marthe and Feda agree to continue their investigation. They begin by mapping the castle and conducting a sonic survey of the walls. Marthe's investigation of Eden's room leads him to discover a hidden diary, which contains unsettling entries suggesting a pattern of victims and impending death.
