After being saved by Subaru, Rem develops feelings for him. She tends to be aggressive in her approaches, often asking him to praise her, and will do anything for him, such as turning a blind eye to certain actions. She also cares for his well being, deciding to take Subaru back to the mansion to see Emilia, and almost left Lugnica with him after debating whether taking him back to the mansion would actually be a good thing.
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, Ram still believes that her sister is much greater than what she can ever achieve.