Pretty Guardian Sailor Moon, Vol. 4

A new group calling themselves Black Moon is after Usagi and the rest of the Sailor Guardians, wielding a new power known only as the Malefic Black Crystal. Chibi-Usa may be the key to it all, but to find the answers and rescue her kidnapped friends, Usagi will have to journey through time to the 30th century and discover what fate has in store.