Pretty Guardian, Sailor Moon. 8

"Chibi Usa's sickly friend Hotaru isn't just Sailor Saturn, Deity of Destruction. She's also possessed by Master Pharaoh 90. Facing this cataclysmic power will be impossible-- unless Sailor Moon can unite the powers of every Guardian of the Solar System. Then, when the moon eclipses the sun, a mystical unicorn begs for help. An elaborate ship floats through the sky, and Usagi and Chibi-Usa have trouble seeing eye to eye" -- from Random House web site.