Birthday: October 13
Ruby Moon is one of two magical guardians created by Eriol Hiiragizawa. Serving as the counterpart to the original guardian Yue, Ruby Moon is genderless but chooses to present as female. When Eriol transfers to Tomoeda Elementary, Ruby Moon assumes a false form named Nakuru Akizuki and enrolls in Seijou High School, joining the same class as Toya Kinomoto, Sakura's brother, and Yukito Tsukishiro, who is the false form of Yue and unaware of his true identity.
As Nakuru Akizuki, she frequently acts as an annoyance, deliberately interfering whenever Toya tries to discuss Yukito's diminishing energy. She claims she wants to consume Toya's energy herself, though it is never explained why she needs it or why she couldn't simply take it. Once Toya manages to speak with Yue and gives him all of his magical energy to sustain Yue’s life, Akizuki ceases her pursuit.
In the final battle, Ruby Moon faces off against Yue and initially seems to be winning. However, Yue ultimately prevails due to his stronger determination and desire to protect Sakura.
In the anime adaptation, Ruby Moon is voiced by Ryoka Yuzuki. In the English adaptation, Cardcaptors, both her true form and false form are referred to as Ruby Moon, and she is voiced by Willow Johnson.
