Rem/Relationships

Natsuki Subaru
When the first two met, their relationship was hostile as Rem could sense the scent of the Witch of Envy emanating off of him, causing her to be suspicious of him. This would lead to two times she would be personally responsible for Subaru's death and subsequent fear of her afterwards. After she dies from the curse Subaru died from initially, Subaru remembers the compassion she and her sister showed him while he was sleeping and resolves to save Rem by using Return by Death. When he confirms the source of the curse, he works with Rem to protect the villagers and ends up saving her from the Demon Beasts at the cost of getting cursed again. This would lead her to attempt to destroy all the Demon Beasts at the cost of her own life until Subaru and Ram were able to return her to her sense and kill the Demon Beasts themselves. Afterwards he would convince her to let go of her past resentful feelings and look to the future.

After being rescued by Subaru, both physically and emotionally, Rem quickly develops strong romantic feelings for him. In her own words, he becomes a hero in her eyes, and feeling responsible for her importance to him, Rem takes on the functions of moral support and combat protection for Subaru. Such as when she restrains his despair and returns Subaru's faith in himself before the final battle of the 3rd Arc, arguing that the person who saved her and who she loves cannot despair and give up. Later, they semi-seriously agree that if Subaru can persuade Emilia, then he will make Rem his second wife, and Subaru even confesses his love to her in both the web and light novels.

Nevertheless, Rem suffers in battle and falls into a coma before Subaru manages to tell Emilia about their idea. Considering this development of events to be his fault, Subaru is even more imbued with the idea of making Rem his wife, or at least recognizing her as his beloved.

Although Rem was technically absent from the main events from Arc 4 to Arc 6, her rescue has consistently been one of Subaru's main goals and motivations. To such an extent that Subaru repeatedly mentions her along with Emilia as the girls he is in love with, and when Carmilla, the Witch of Lust, took on the appearance of Subaru's closest and most important person in the Sanctuary, that also turned out to be Rem.

Subaru manages to bring her back from her coma at the end of Arc 6, however, it is revealed that she suffers from amnesia.

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 L Mathers
Roswaal took Rem and Ram under his wing and is shown to deeply care for them, as seen when Rem died of unknown causes and he immediately suspected Subaru for her death (he was even prepared to kill him, much like Ram). Due to Lye Batenkaitos eating her name and memories and leaving her in a comatose state, Roswaal no longer remembers her, though he does allow Subaru to let her stay in the mansion.

Emilia
Rem submits to Emilia as one of the maids of the Roswaal manor, and always refers to Emilia with the prefix -sama and unquestioningly obeys her orders, being really close to her only under the influence of alcohol. Although they are technically rivals for Subaru's heart, she declares that due to her loyalty and respect for Subaru's feelings, Rem will not fight her for her beloved. For this reason, she refuses to run away with him in the main story, believing that if Subaru chooses her at the cost of giving up the fight and saving his loved one, Subaru will be discredited and even destroyed in her eyes. At the same time, she agrees to become Subaru's second wife if Emilia agrees to this idea.