Following Father Olba's failed attempt to kill King Satan and Emilia on Earth, word of their survival begins spreading across the land due to the testimony of Emeralda Etuva and Albert Ende who had returned to Ente Isla after verifying the whereabouts of the Hero and Demon Lord. Crestia Bell catches wind of these new developments and alerts her superiors of this new development, much to the surprise of the clergy members present. Father Robertio expresses concern, but comes close to fainting when she elaborates on Olba's betrayal against the Church. She then questions if their former colleague should be considered a heretic, to which he reluctantly affirms. Crestia Bell also confirms that Emeralda had returned to the Holy Saint Aire Empire and was responsible for the news of Emilia's survival reaching the ears of the people, the magician's high status having allowed her to spread the news quickly. Due to the Church having officially reported her death to the public, the High Priests are noticeably bothered by this new development, knowing that the Institution's previous actions had already tarnished the reputation of the Church. Unable to come up with a reasonable countermeasure, Father Robertio then prompts the Head Inquisitor to come up with her own solution for this problem, to which she agrees.
Following this meeting, Crestia Bell is dispatched to Earth alongside the Archangel Sariel to execute the Devil King, though she remains largely unaware of her collaborator's goal to take the Sacred Sword from the Hero Emilia. Before beginning her mission, she attempts to learn about Japan by viewing classic historical dramas, making her knowledge of their culture and etiquette vastly outdated. Upon arriving in Tokyo, she adopt the alias of "Suzuno Kamazuki" and begins her investigation in Satan's whereabouts by questioning Olba Meyer, who at that point had been taken into police custody for his previous criminal activities. From him, she receives a vague idea of the Demon Ruler's lifestyle and address, though she becomes concerned when he mentions that Emilia had joined forces with King Satan. Planning to get close to her target under the guise of a friendly neighbor, Crestia Bell establishes contact with the landlady, rents the apartment one door down from the new "Devil's Castle", and moves into Villa Rosa Sasazuka. While heading up the stairs to the second floor apartments, she trips and falls, landing in Maou's arms before fainting.
Suzuno formally introduces herself to the Demon trio as the new neighbor, bringing a box of udon noodles with her as a welcome gift. While her archaic manner of speaking confuses Maou, he and Ashiya kindly return her introduction and accept the gift gratefully. Suzuno mentions that she had been in contact with the house's owner and had already learned their names, but is stopped before she can show them Miki Shiba's letter due to the demons' fear of seeing another bikini pic of their morbidly obese landlady. Urushihara then greets her without much enthusiasm, but Maou is quick to mock him for his unhelpful personality and general laziness, causing the pair to bicker while Suzuno politely excuses herself.
Later that afternoon, she returns to the "Devil's Castle", kindly helping Maou's group with the daily chores while teaching Hanzō Urushihara how to handle basic household tasks. She continues her lesson on home economics by showing him how to prepare meals, admonishing the lazy tenant for his lack of motivation, much to Ashiya's approval. When Suzuno prepares to fetch some ginger from her own apartment to use in a recipe, she discovers Emi Yusa lurking in the doorway, causing the hero to tumble down the stairs and into Maou as she flees. After they reconvene in the apartment house, Suzuno apologizes for startling the redhead during their brief encounter in the entry, but Emi shrugs it off as an accident caused by her own carelessness. When the group takes note of Ashiya lying sick on the floor, Suzuno claims her udon noodles might have been the culprit for his current state, but he kindly refuses to let her take the blame. The Church Inquisitor then introduces herself to Emilia as Suzuno Kamazuki, claiming to be from an old-fashioned foreign family to explain her lack of familiarity with Japanese society. During another argument between the hero and her nemesis, Suzuno questions whether or not Emi has an intimate relationship with him. The hero is outraged by her assumptions, relieving Crestia Bell, who had been under the impression that Emilia had joined forces with the Devil.
Emi mistakes the other girl's reaction as a sign of jealousy, instead believing that the female tenant is in love with Maou. She quietly asks Suzuno if she is after the Demon King, but the dark-haired girl hastily pulls her from the apartment in a nervous frenzy, looking horrified at the prospect that Maou could have overheard them. Emi kindly advises her to stay away from Maou for her own safety before handing her some written contact information in case something were to happen between her and the neighbors, the Church Inquisitor interpreting the gesture as an alliance to help her kill the Demon King. Emi then departs the scene, both girls remaining unaware of the other's intentions. Suzuno later makes a huge two-layer bento for Maou, the top containing New Year's dishes and the bottom containing rice decorated with a heart. Maou opened it in front of Chiho, which lead to the same misunderstanding with Chiho Sasaki as well.
The next day, Emi accompanies a jealous Chiho to check on the three demons again, though by the time they arrive at the apartment, Suzuno is already there preparing another meal for her fellow boarders. During the subsequent visit, Emi also notices Suzuno's old-fashioned manner of speaking and learns that she has yet to find a job, though she expresses surprise when Maou invites her to apply at MgRonald's. Hearing that Suzuno primarily dresses in kimono and doesn't own any modern clothing, Chiho suggests they take her shopping, to which Emi agrees. The hero later accompanies takes her shopping to buy some modern clothes, but Suzuno found that she had forgotten her purse, and on the way back to retrieve it, happens to see Chiho confess her feelings to Maou. She unwittingly teases the teenage girl, causing Chiho to ride off on Maou's bike in her embarrassment. The undercover inquisitor is surprised by Maou's concern for his co-worker's safety and his kind offer to walk her to the train station.
Suzuno later meets up with Emi at the train station, expressing a lack of knowledge concerning modern transportation and Japanese currency in the process. Her ignorance leads Emi to question where she is from, with Suzuno bluntly replying that she came through the Gate. Realizing that their new friend is from Ente Isla, Emilia expresses shock, while the Church Inquisitor is surprised that she was not already aware of the fact. After some bickering, the blue-haired woman claims to have interpreted Emi's questions about Maou and sharing of contact information as signs that the hero knew of her true identity and was planning to form an alliance. Suzuno also reveals that her own cautiousness was due to a rumor that Emilia had joined forces with the Devil King, but Emi clears up the misunderstanding by informing her that it was only a temporary alliance to defeat a common enemy. Emi assumes that she was the person who attacked her the previous night, but the vast discrepancies in her attacker's appearance coupled with Suzuno's ignorance of the conflict, indicate otherwise. Upon being questioned again, Suzuno reintroduces herself as Crestia Bell, Head of the Doctrinal Correction Council, but Emi tells her to save the details for their shopping trip.
After helping a confused Suzuno through a day in modern Tokyo, the two settle down in a nearby coffee shop to finish their earlier conversation. During the discussion Emi discovers that Crestia Bell had learned about Japan through the viewing of classic historical dramas, hence her lack of knowledge concerning modern technology and etiquette. Suzuno also explains that her purpose on Earth is to defeat the Demon King and return home and requests her help in this endeavor, however, Emi is unwilling to cooperate with the Church again. Bell deeply apologizes for the recent actions of Father Olba, but the hero still refuses to trust the institution who betrayed her. Emi then advises Suzuno not to interfere with her battle with the Devil, also warning her that Maou will figure out her true intentions should she continue to spend time with the demons, before leaving for work. When the two meet again that evening, it is revealed that Suzuno had bought only traditional clothes after selling some of her easily converted assets at a pawn shop. Suzuno phrases her intentions to observe Maou at his workplace, leading to yet another misunderstanding from Emi's friend and colleague Rika, who incorrectly assumes that Maou had some kind of romantic relationship with both girls.