Amalie Mainbach

Amalie Mainbach is the widowed sister-in-law and mistress of Wendelin Baumeister. She was married to Wendelin's oldest brother Kurt Baumeister, prior to his death.

While married to Kurt, she took his surname, Baumeister. However, after his death she chose to revert to using her maiden name, for both herself and her children, to avoid some of the stigma and ostracization associated with her deceased husband's actions.

Personality
Amalie is a very kind and soft-spoken woman. She is abundantly aware of her social standing and how women don't typically have a voice in matters and, therefore, she stays out of the matters despite being one of the best educated people in the territory.

Because of the inability to connect on an intellectual level with so many within the Baumeister Knighthood, she cherishes contact with her brother-in-law Erich, who is about as educated as she is, as well as her other brother-in-law Wendelin, who despite being 12 years her junior, is far more knowledgeable. When they are away from the territory, she writes and receives letters as often as the merchant caravans allow.

Synopsis
Amalie is the daughter of a Knight peerage household and her marriage to Kurt was arranged between the households. She was 18 at the time, making her 13 years older than Wend and six years younger than Kurt. She bore Kurt two sons named Karl and Oskar.

A few months after her husband's death, her father-in-law, Artur Baumeister, arranged for her to become a sex-teacher for the soon-to-be-married Wendelin, but they fell in love and the relationship continued after his marriage. She became one of his mistresses and eventually gave birth to his daughter, Rosina.

Abilities
Amalie has normal human mana, which means she cannot use magic. At one point in the novel, Wend discovers that sexual relations with him cause the other wives to increase in mana beyond their previous upper-limits, however he notices no such increase in her mana, causing him to surmise that a person must have magical talents first to allow that effect. He is somewhat saddened that even with such a discovery she will not be able to learn magic.
 * The discovery that intimate relations between magicians of different power levels allows for an increase over previous mana capacity caps is considered a critical secret that could dramatically alter politics from local to international levels if it were to become more widely known; for this reason, the only people who know about it right away are Wendelin, his wives, Amalie, his retainers Erwin and Rhodrich, Brantark, and Christoph von Armstrong; Margrave/Duke Bleichröder and King Helmut are also informed a short time later.

Amalie was raised to be able to read, write, and perform even relatively complex math calculations, and can do so at a level similar to that of fifth son, Erich. Once Erich and Wend leave the domain, she and the main-village chief, Klaus, are the only people at the head of the territory that can reliably do so. By comparison, her husband Kurt's scholastic ability is considered particularly poor even in comparison to the poor educational state of the territory.
 * The fact that she can read and write is why, in both the novel and anime, the older brothers comment to Wend while at Erich's wedding in the capital that the letter from Artur indicating they have no money to send wedding gifts was almost certainly written by Amalie.

Kurt Baumeister
Amalie is the widowed ex-wife of Kurt. She bore him two sons.

Amalie met Kurt for the first time on their wedding day, when she was 18. Since this was an arranged marriage between two different Knight peerages with only sporadic contact, this was not seen as unusual.

According to her own account, she was treated well by Kurt for the first three years, but then mostly ignored for the remaining six in favor of him having a mistress once she had provided him with heirs. She is not sure whether he never really loved her, or whether he simply stopped loving her at some point, and feels inclined to believe the truth is somewhere in the middle (that he genuinely cared at first but never really loved her). She comes to this conclusion because he seemed to sincerely act like a proper and caring husband at first, but then his personality turned toxic shockingly quickly.

At the time Kurt died, she was 27. She wasn't directly concerned about her own personal future, but immediately became deeply concerned for the future fate of her two children, both as a mother and because at least one of them would have likely been heir to the Baumeister Knight peerage after Kurt.

Wendelin Baumeister
Amalie met Wend for the first time on the occasion of her wedding to Kurt. Over the next six years, she interacts with him cordially, and respects his ability to read and write, which is much better than even her own. When he leaves the territory at age 12, she gets permission from Artur to write occasional letters to be transmitted to Wend and/or Erich via the merchant groups, which Duke Bleichröder sends to the territory three times a year out of a sense of obligation.

After her husband's death, she is mostly concerned for the fate of her children, as the widow and children of an attempted assassin can expect to be judged harshly by society. Instead, Wend, who was made a count immediately following Kurt's death, makes a sincere promise to her that they will be treated well. He also promises that he will bestow upon both of them a knight's peerage when they come of age, as the king had granted him the authority to hand out two of the peerages that were previously held by Baron Rückner and his noble allies, as they had perished while conspiring and manipulating Kurt in his attempt to kill Wend (in the novel, he promises to grant one to the older brother, with the younger brother becoming the junior commander, and the king granted permission for him to distribute all 12 vacated noble titles of Baron Rückner's allies).

About two months after Kurt's death, Artur and Duke Bleichröder attempt to find a woman appropriate to teach Wend about sexuality before his pending marriage to his first five wives. The idea is that nobles need to be able to produce an heir, and thus need to be experienced sexually. This is particularly notable, as for more important nobles, the wedding night will be observed by a maid or servant to ensure the wedding is properly consummated. For less-important nobles, such as Artur himself, a book detailing sex is provided instead. The role of sex-teacher is typically given to a woman who is a widow, due to their experience but also because they would not be seen as having an extramarital affair. The teacher is paid, for their time and effort and also as part of a promise to keep the relationship secret both from society and the soon-to-be wives themselves, even though it is tacitly acknowledged by society and the wives are often aware but merely accept it. Because of this secrecy, the "arranged women" are only to be with the noble until the wedding, and both sides are expected to completely end the relationship at that point.

After failing to find any other appropriate candidates, Artur decides to ask Amalie if she would be willing to take the duty, expecting her to decline. She accepts however, due in part to her desire to ensure that Wend holds up his promise to confer the peerages to her children, but also because she genuinely seems to like him and think of him as a kind and sweet person. A small, private hut, located in Paul's new territory, is provided for their trysts. To her pleasant surprise, however, Wend actually courts her, like a real romantic relationship, by taking her out on dates to the capital city via magic. Using magic to hide their appearances, he would buy her gifts like sensual underwear. He would also purchase luxurious furniture and decor for the hut such as curtains, a nicer bed, and a quality bath and shower. She notes that his care and attention makes her feel "like a woman again," a feeling she had been convinced was gone for good.

Because of that, despite societal expectations, they did not end their relationship once he marries, and she instead transitions from being his "arranged woman" to an actual mistress. Their feelings for each other progressively grow into genuine love and affection, though their rate of contact decreases as he necessarily divides appropriate time for his actual wives. Wend's wives are aware of their relationship, and Elise, as head-wife, gives her tacit consent as long as he does not spend more than one day a week with Amalie (as his number of wives later grows, even once a week becomes too frequent). They continue to go on romantic outings in places like Breitburg or the capital, and not just as covert sexual rendezvous but as genuine dates, mirroring the same treatment he gives to all of his wives.

In time, her relationship with him eventually gains full approval of all his wives, rather than just the tacit acceptance of Elise, and she eventually moves in with them in order to remain close to Wend, while her two children she had with Kurt, were both sent to live with the Mainbach family to grow and train to eventually inherit the new title and territory. Amalie now serves as the Baumeister mansion's head housekeeper, similar in station to the formal maids and servants but distinct in that she is not officially one of them.

Trivia

 * Amalie's closest companions are Therese and Lisa - the trio are also the three oldest members of Wend's harem.