Sailor Moon is a Japanese manga series written and illustrated by Naoko Takeuchi. It was originally serialized in Kodansha's sh?jo manga magazine Nakayoshi from 1991 to 1997. The series follows the adventures of a schoolgirl named Usagi Tsukino as she transforms into the eponymous character. She leads a group of comrades, the Sailor Soldiers, called Sailor Guardians, as they battle against villains to prevent the theft of the Silver Crystal. The franchise has generated $13 billion in worldwide merchandise sales.