Chibiusa Tsukino is the Crown Princess of the 30th century kingdom of the Moon, Crystal Tokyo.
She is the first princess of the Silver Millennium known as Small Lady by the Sailor Senshi of the future. The Black Moon Clan call her Rabbit. She travelled through time so she could save her mother. She is really good at the Sailor V game. Her best friend is Momoko Momohara.
Chibiusa falls from the sky through a time portal and lands on top of Usagi's head, and kisses Mamoru in the process. She introduces herself as "Usagi Tsukino" and asks Usagi why she has the same hairstyle and the same name as her. Realising that she's found the person she's looking for, Chibiusa pulls out a gun and threatens Usagi to give her the Silver Crystal quickly. Later she uses the mysterious magic of Luna-P to put a spell on Usagi's Earth family in accepting her as their relative.
Usually the rate of aging halts after adulthood due to the power of the Silver Crystal but Chibiusa is 900 years old with the body of a little girl. Often compared to her mother, the Queen, who she looks up to very much.
Chibiusa is unable to use the Silver Crystal, has no power of her own and cannot transform.
The Black Moon Clan capture and transform Chibiusa into Black Lady.
Distraught over the death of Sailor Pluto, Black Lady's Black Crystal Earrings shatter and she is transformed back into Chibiusa. She finally finds her power therefore she can now transform into Sailor Chibi Moon.