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.

Trivia

 * Amalie's closest companions are Therese and Lisa - the trio are also the three oldest members of Wend's harem.
 * She is encouraged by Therese to do her best to get pregnant after all of Wend's wives have children.