Sailor Moon is a Japanese manga series written and illustrated by Naoko Takeuchi. It was originally serialized in Kodansha's shōjo manga magazine Nakayoshi from 1991 to 1997; the 52 individual chapters were published in 18 volumes. The series follows the adventures of a schoolgirl named Usagi Tsukino as she transforms into Sailor Moon to search for a magical artifact, the "Legendary Silver Crystal" (「幻の銀水晶」, Maboroshi no Ginsuishō, lit. "Phantom Silver Crystal"). She leads a group of comrades, the Sailor Soldiers, called Sailor Guardians in later editions, as they battle against villains to prevent the theft of the Silver Crystal and the destruction of the Solar System.