As Mamoru and Usagi lean in for a romantic kiss, a small girl with bright pink hair falls out of the sky and lands on Usagi, demanding the Legendary Silver Crystal from her. The girl, also named Usagi, quickly gets nicknamed "Chibiusa". Usagi starts to become suspicious when she returns home and her family identifies Chibiusa as her cousin. Meanwhile, a new enemy, the Black Moon Clan, comes to Tokyo looking for Chibiusa.