Chibiusa was the civilian identity of Sailor Chibi Moon, and she appeared in the anime and manga series. Her real name was Usagi, but to prevent confusion, people called her "Chibiusa" ("chibi" (ちび) meaning "small person"; "usa" (うさ) being short for "usagi" (うさぎ; "兎" in kanji), meaning "rabbit"). In Crystal Tokyo she also went by the name Usagi Small Lady Serenity.
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 900, 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....