Rem is one of the twin maids working for Roswaal L Mathers. She tends to speak in a superficially polite manner and sometimes acts without thinking. She holds both worshipping respect and guilt toward her sister for an incident in the past; because of this, Rem tends to think of herself as inferior.
After Subaru saves her, she falls deeply in love with him, becoming one of his most loyal followers. Rem will stick with him no matter what happens, even if Subaru rejects himself.