It is based on a series of fantasy novels written by Japanese author Fuyumi Ono and illustrated by Akihiro Yamada. The first entry in the series called The Twelve Kingdoms: Sea of Shadow was published by Kodansha in Japan in 1992; the last Kodansha volume was released in 2001. In 2012, the series was resumed under the Shincho Bunko line from Shinchosha. Shinchosha has also begun reprinting the older volumes with new cover and interior art from Akihiro Yamada. The first new publication of the series in six years was released in 2019.