Natsuki Subaru
After being rescued by Subaru, both physically and emotionally, Rem quickly develops strong romantic feelings for him. In her own words, he became a hero in her eyes, and feeling responsible for her importance to him, Rem took on the functions of moral support and combat protection for Subaru.
Ram
Throughout their childhood, Ram had always been superior to her in every way. Growing up in her sister's shadow, Rem greatly admired her older sister, but also had some lingering resentment and feelings of self-inferiority. However, that resentment turned into guilt after Ram lost her horn. Even afterwards, Rem still believes that her sister is much greater than what she can ever achieve.
In general, Rem and Ram are as close as expected from the twins. For example, although they have quite different personalities, the sisters easily understand each other and even instinctively synchronize their thoughts or actions, if necessary. This is particularly noticeable on Rem's part, who has a platonic sister complex towards Ram and is even openly jealous of her to Subaru when she thinks they are in love with each other.
Roswaal Mathers
Roswaal took Rem and Ram under his wing and is shown to deeply care for them.
Emilia
Rem submits to Emilia as one of the maids of the Roswaal manor, and always refers to Emilia with the prefix -sama. They have rarely interacted with each other but Emilia has shown her caring nature for Rem by hugging her while they were drunk.
Mabeast
Demon Beasts are any number of organisms that are able to sustain themselves off of mana and have origins of creation by the Witch of Gluttony. Under most conditions, they are larger and stronger than regular fauna and typically possess often hazardous magical abilities.
Roswaal Manor
Roswaal Manor is the name given to two mansions owned by Roswaal Mathers. One of them, dubbed the old Roswaal Manor, was a reserve mansion located near Arlam Village. The second manor, dubbed the new Roswaal Manor, is the main residence of the Mathers family, located near the Industrial City of Costuul. The manor is a giant white house with five watchtowers with the fifth one being the center one, a giant garden and a black roof. It has a massive basement that is almost as big as the surface of the mansion itself.
Entryway
Upon entering, it was noted that the mansion retains great elegance. There are two pillars with a pair of lamps each. In addition to having high class designs, there are lights near each door, as well as vases with flowers. On the road there are two routes to the sides, right and left, and stairs to go up to the next floor.
Kitchen
In that place the servants of Roswaal prepare breakfast, lunch and dinner. It is full of plates, pots, jars, rollers, knives and other things that can be used to prepare food. In case they need to buy more food, they go to a market and transport the products by putting them in a barrel.
Bathroom
The bathroom can be used a sauna and has few marble pillars in it. It has a bath in the center of the room with a golden pillar in the center of the bath.
Washbasin
It is used for personal hygiene, it contains the same white washbasin, a toilet with a brown lid and a mirror decorated with a golden frame.
Guest's Room
It is the place where the head invites their visitors to talk. It is observed that it has three green furniture and a small rectangular table in the center, to its surroundings there are also windows with light green curtains. It is noted that there is a fireplace and above a picture showing a drawing. User is staying here as they recover from their injuries.
Dining Room
In the dining room, all the people in the mansion gather to eat. In this place there is a large table covered with a white tablecloth, on each side there are several chairs, and regardless of the time, lights are placed on the table. The wall is green and has certain white spaces. Behind the table there is a figure in a painting, possibly a relative of the Roswaal family.
Garden
The garden is located on the outskirts of the mansion, it has several characteristics, such as that it is full of grass, besides there are also several paths where you can walk. On the sides you can see small fields full of flowers, you can also see some large trees and other small trees, as well as bushes. There are also places to rest.
Kingdom of Lugunica
The Dragon Kingdom of Lugunica, is one of the world’s Four Great Nations. It is a monarchy, historically ran by the now-extinct Lugunican Royal Family. It borders, in one way or another, the other three Great Nations. Lugunica is a geographically large nation with a massive population of approximately 50 million individuals, with its territories able to support multiple environments and multiple climates. It is home to many races and ethnic groups and the nation's history spans at least one thousand years. It celebrates its nominal day of foundation on the 25th of the in-universe month, Marshba. The closest person to being the head of state in the absence of the monarch is Miklotov McMahon, who has worked in a position of high office for the greater part of forty years.
Despite economic recovery and relative peace and stability across most of the country, the contemporary Lugunica is negatively characterized by internal strife, racial tension, economic hardship among the disadvantaged, desperation for new decisive leadership by both the public and the ailing transitional government, and more recently, religious cult extremism and terrorism.