Chibiusa belonged to the future, 30th-century Crystal Tokyo, and travelled back in time to 20th-century Tokyo initially to save her mother and again later in the story for training as a Sailor Senshi. She was the daughter of Neo-Queen Serenity and King Endymion, the future forms of Usagi Tsukino and Mamoru Chiba respectively, and the granddaughter of Queen Serenity. She had a guardian device called Luna P, and a grey kitten named Diana, who was the daughter of the moon cats Luna and Artemis.

When she first arrived in the anime continuity she was around 6 years old, while in the manga continuity she was chronologically 901, but still mentally and physically 6 years old. The delay in her aging was due to the power of the Silver Crystal and the fact that her own powers as a Senshi had not been fully awakened.

In the anime, before she gained the ability to transform into Sailor Chibi Moon, Chibiusa also had the power to emit a column of extreme energy from the crescent moon symbol that could appear on her forehead. She tended to do this when she was alarmed or scared, and the energy column was visible from a distance, which meant that the Black Moon Clan used it as a way of tracking her.