The Past Returns
Usagi's Awakening: A Message from the Distant Past
Usagi no kakusei! Chokako no messeji
"Sailor Venus finds the Dark Kingdom's hideout. The Sailor Guardians fall into Kunzite's trap, which hurls them into the past. The girls find themselves in a world called Silver Millennium, where they meet Queen Serenity, the mother from Usagi's past life." (source)