Once the Princess was executed after the revolution, many dignitaries began seeking asylum after the Kingdom of Lucifenia lost its function as a nation, although it was supposed to only be temporarily subordinate to the western sea island nation, Marlon. But a year later, the king of the Marlon country, Kyle, forcibly annexed the Kingdom of Lucifenia territory and, by obtaining a territory on the continent, he could begin an invasion of the surrounding countries. Four years later, as the situation in the old Lucifenia territory became unstable again, one girl was standing. Leaping from her homeland as if running away from home, the sheltered girl, Yukina, flew around the outside world with her notebook in one hand and a pen in the other. She wanted to "know more about the truth of this world". Following the mystery, did she obtain the "truth"...?
Note: This summary is incomplete; improved summary pending until full translations are acquired.
One day, Rin stands at the beach lamenting over her past. As she does so, she observes a rich woman berating her servant over getting them lost. The woman soon recognizes Rin as a girl from the Held Monastery and asks for her aid getting to the place; after Rin agrees, she explains that she is looking to visit her friend, Clarith.
Elsewhere, Yukina Freezis takes in the sights in former Lucifenian city Retasan, intending to move through to Beelzenia; during this time she encounters a blonde-haired female soldier. The girl thinks back on the events of the last five years, including how Lucifenia had been forcibly absorbed into the Kingdom of Marlon, and how she had run off from home to find the true story of the Daughter of Evil.
After attempting to pass through to Beelzenia, Yukina is blocked at the gate; she returns to her hotel to eat lunch and in the process meets the soldier she had run into earlier. The two begin to talk over lunch, discussing the source of the tensions between Beelzenia and Marlon as well as the Blue Kingdom's imperialist policies when the soldier is called away. Yukina learns that she is Commander Riliane Mouchet.
Yukina spends more time with Riliane, also known as Lily, over the next five days, learning more of her character and history in that time. Lily discusses how to get Yukina into Beelzenia before the girl requests to send a messenger to the country. Eighteen days later, Lily hurries Yukina out of Retasan, relating that the messenger's request for the permit to enter Beelzenia has been issued at the cost of alerting her superiors. After directing the girl to go to Rucolebeni, the two part ways.
After arriving in Rucolebeni, Yukina sets out to visit the Conchita Mansion located nearby, thinking back on her research into the Seven Deadly Sins and Elluka Clockworker's relation to them. She remembers how Elluka and Gumillia had stayed with the Freezis Family many years earlier and how the two are now fugitives of King Kyle's Witch Hunt order along with Germaine Avadonia. The girl encounters Gumillia while exploring the mansion. The next day, the two head out together and catch up; Yukina learns that Gumillia is the adviser to the Beelzenian Emperor and that Elluka is missing. While following Gumillia to the Langley Unit Garrison, Yukina encounters its commander, Chartette Langley.
Chartette then escorts the two the rest of the way to the garrison, where she explains the troops' history as former members of the Lucifenian Resistance. At Yukina's request to meet Germaine Avadonia, Chartette takes them to first meet York and Minage. Gumillia departs after speaking with the two for some time, while Chartette is called upon by Minage to aid him in other matters; Yukina steps out alone and encounters Germaine nearby. She questions the swordswoman over her fugitive status from Marlon and suspected involvement in Michaela's death; after Germaine denies any involvement, Yukina decides to stay in Beelzenia to further pursue the truth.
Much later, after meeting with the Beelzenian Emperor, Yukina takes a tour of the country with her guide, the Duke Oruhari, investigating Banica Conchita. After she learns what she can about the famed warlord, Yukina bids Oruhari farewell and departs with Chartette the next day, hoping to meet Gumillia in the Imperial City. While passing through a cemetery, the two encounter a previous colleague of Chartette's, Ney Phutapie, wearing a Marlon commander uniform.
While speaking with Chartette and Yukina, Ney announces that Marlon has declared war on Beelzenia, also revealing herself as the Marlon head of espionage and Mariam Phutapie's murderer. She then inexplicably brings out a bottle of wine and a glass; pouring the wine from the glass to the ground. Suddenly, the tombstones start to shake and the earth begins bulging. Fearing for their lives, Yukina and Chartette run away towards Rucolebeni.
Arriving in town and attempting to comprehend what they had seen, the two encounter a pale monster in the streets. After a fruitless attack on the creature, they take shelter in a local bar, finding a drunken Germaine inside. Chartette then exits to fight the monster while Yukina witnesses the bartender recognize it as her deceased son.
After the monster is defeated, the two take its body to the Royal Palace, where they are followed by Beelzenian troops pursued by an army of the creatures. Afterwards, Yukina meets with Duke Oruhari, who informs her that the monsters are in fact an army of undead soldiers. As a result of the threat, the city is put on lockdown; with Gumillia too busy to speak to her and Chartette leaving to fight the soldiers, Yukina is confined to her room.
Yukina later escapes the Imperial City to aid the Langley Unit in Rucolebeni. After an attack, she is discovered by Germaine; while chastising the girl, the swordswoman is interrupted by the arrival of Lily, who has left her position as commander of Retasan Fortress and wishes to speak with the Emperor. Later, outside the meeting, Gumillia discusses Ney’s power over the undead soldiers and the Glass of Conchita with Yukina. When Gumillia is called away, Lily returns from her meeting and chats with Yukina for some time; during the conversation, Yukina is informed that Ney now commands Retasan and that a counterattack has been issued against the fortress city.
Back in the Imperial City, Yukina requests that the Freezis’ family’s retired butler, Bruno, explain the deadlock between Beelzenia and Retasan as the Empire prepares to attack. After further speaking with him, Yukina visits Germaine in the Rucolebeni bar, the swordswoman having chosen not to participate in the battle. While there, Yukina witnesses Lily criticizing Germaine for refusing to aid the counterattack, this leading to a heated discussion on the women's views of revenge, as well as Germaine's role in the Lucifenian Revolution. Three days later, Yukina receives another report that Beelzenia’s victory in capturing Retasan is assured.
Two months after the city is captured, Yukina visits Retasan again in hopes of finding Gumillia, who had left some time before to find Ney. She finds the girl just as she prepares to depart to Lucifenia, and learns that she had hired Germaine as a bodyguard for the trip. After inquiring after their motivations and arguing the danger of their plan as wanted criminals, Yukina invites herself along on the trip to aid them, using her family’s relationship with King Kyle Marlon.
Meanwhile, in Marlon occupied Lucifenia, King Kyle debates the state of Marlon's new regime with a subordinate, General George Ausdin. Later, he meets with Ney Phutapie, along with the rest of the Special Maneuvers Task Force; during their discussion, the girl informs him of her plans to return to Marlon for further instruction on wielding the Glass of Conchita. She leaves, giving Kyle the remaining members of the task force under his orders.
Two weeks later, Kyle attends a banquet held by Corpa; during the guests' entertainment, Kyle develops a headache and goes outside. He is soon approached by a young woman, whom he eventually recognizes as Yukina Freezis. After conversing for some time, Yukina tells the king that she will be visiting the palace tomorrow and leaves; soon after, Kyle also departs.
The next day, Kyle receives Yukina and her two masked companions in his throne room. After exchanging pleasantries and explaining her new companions, Yukina speaks to Kyle on trade matters, claiming to be Keel's proxy. Realizing her deception, Kyle feigns ignorance and offers for her to see the palace, ordering Clive to send a message to Keel after she leaves.
That evening, Kyle encounters Yukina in the Heavenly Yard and the two fall into talking about their most treasured items, Yukina's notepad and Kyle's mirror as well as a third, classified item. When they finish, Kyle learns Yukina is staying in Rollam and arranges for her to stay in the Lucifenian palace instead. That night, Kyle looks over Nicolay Tolle's paintings until he is approached by a guard; the two speak before being interrupted by an explosion, and Kyle is prompted to investigate.
Moving to Yukina's room, Kyle encounters Clive and learns the explosion was caused by the Special Maneuvers Task Force in pursuit of a target. Inspecting the room, he asks after Yukina and then tells Clive to rouse the rest of the guards to find her and her companions; Kyle then searches the palace with Clive before becoming drawn to his own bedroom by another explosion.
Upon entry, Kyle discovers the intruder surrounded by the Special Maneuvers Task Force. Recognizing her armor, he asks the others to withdraw. After the thief is revealed as Germaine, the two converse and Kyle confronts her over Michaela's murder, citing a conspiracy between her, Elluka, and Gumillia. Kyle then becomes further influenced by the demon and stalls; as he orders Clive to kill Germaine with the Task Force, the former Resistance leader escapes.
Following the call of the mirror, Kyle runs to Riliane's room and passes through the secret passage into the stables, where he encounters Yukina and her other companion, Gumillia. Kyle steals the hand mirror from Yukina and the three of them argue over his possession by the demon until the king begins to transform. Attacking Gumillia as she attempts to intervene, Kyle sprouts wings and flies off into the night sky.
Conceptualization and Origin
- The word praeludium is Latin, meaning "prelude", an introductory performance preceding a more important one, referencing its sequel.
- Originally, Lily was planned as the main character of the story with Yukina as a supporting role but was later changed so that the story would be told from Yukina's perspective.
- Originally, the origin of Germaine's birth and how she was adopted by Leonhart was planned to be included in the light novel but was cut for convenience; mothy later explained that this was going to be through a scene where Yukina and Germaine discover the village where she was kidnapped from.
- In retrospect, mothy considers the original plan to have an entirely new character, Lily, taking the lead somewhat contrived and is satisfied with the change to Yukina.
- The novel was complemented with a benefits booklet titled "The Memorandum of Evil", containing an interview with Akuno-P, a map of Evillious, and concept art for character designs.
- Several of the places Yukina mentioned visiting include the ruined mansions of Duke Venomania and Banica Conchita; these settings would later be featured in the Deadly Sins of Evil series.