"No matter what happens, even when it looks like you're gonna lose, when no one believes in you, when you don't believe in yourself, I will believe!"

Rem is a maid in service of Margrave Roswaal L. Mathers alongside her sister, Ram. She is one of the main supporting characters of Re:Zero, with major roles in Arc 2, Arc 3, and Arc 7, and a supporting role in Arc 8. During the first half of Arc 2, she also served as the secondary antagonist.

While initially distrustful of Subaru, she eventually opened up to him and even developed strong feelings for him after he saved her. However, at the end of Arc 3, she had her name and memories eaten by Lye Batenkaitos and subsequently fell into suspended animation. At the end of Arc 6, she finally woke up from her slumber following Lye's death, though she now suffers amnesia due to not having yet regained her memories.

Rem was identical to Ram in every aspect, with the exception of her eyes, the color of her hair, and the size of her breasts. Her blue hair was cut into a short bob and parted to fall over her right eye, as opposed to Ram whose hair fell over her left eye. Her large light-blue eyes, pink lips, and soft skin gave Rem a youthful loveliness that Subaru Natsuki found both beautiful and adorable when he first saw her. Rem noticeably had a larger breast size than her older sister. As previously mentioned, Rem's eyes were different to Ram's, as the elder sister's were slightly more slanted. Her delicate frame featured narrow shoulders and stood at 150-hours centimeters tall (or five foot one).

Judging off of her appearance, Rem inherited the color of her eyes from her father and the shape of them from her mother. She also clearly inherited the natural shape and color of her hair from her father. Rem, as a demon, could manifest a small curved-horn on the center of her forehead that was made out of pure pink energy.

Most of the time, Rem wore a uniform issued to her as part of her job in Roswaal's mansion. This maid outfit consisted of a short black dress with white flowery accents, a white apron, white thigh-high socks, black shoes, and a white-and-black flowery headpiece.