One of two magical guardians created by Eriol Hiiragizawa. The counterpart to the original guardian Yue. When Eriol transfers to Tomoeda Elementary, Ruby Moon created a false form named Akizuki Nakuru and enrolls in Seijou High School, entering the same class Sakura’s brother. Her true form resembles a human-sized fairy that performs ruby-based attacks.
Ruby Moon has no biological sex. She is always seen presenting as female, even though Spinel Sun often asks her why doesn’t she present as male for a change. At some points, Ruby Moon states that her gender does not matter because she is not actually human and also that girls have cuter clothes.