The Summer of "Anu": In a summer once every five years, demons in the mysterious Tower of Druaga lose their powers due to the magic spell cast by a god named "Anu". King Gilgamesh, ruler of the kingdom Uruk, uses the appearance of demons as an excuse to invade the tower and find out the construct's secrets. As 80 years passed, the Uruk army managed to fight back the demons and built a fortress city and safe haven on the very first floor of Druaga—Metz Kier. Thus begins the story of a warrior named Jil, who, finding companions along the way, embarks on a quest for the fabled Blue Crystal Rod, a powerful artifact rumored to be in the highest floor of Druaga. However, other competitors, including the kingdom of Uruk itself, want the treasure, all for their own reasons.

A story set in the mid-1800's about a young doctor who has been trained in Western-style medicine and a young samurai who is trying to live up to the old traditions of his class and culture. The story is actually based upon real people - the doctor, Ryo-an, was Tezuka's great grandfather.

The manga series was adapted to anime by Madhouse Studios and premiered in Japan on NTV on April 4, 2000.

During the Second Year of Ansei (1855) in Edo's Koishigawa are two young men, Manjiro Ibutani and Ryoan Tezuka. Ibutani is a low-ranking samurai who is a gifted swordsman and has a straightforward and strong sense of justice. Tezuka has a more carefree attitude. He has an eye for the ladies, but he is passionate about becoming a doctor. The two opposite characters come of age during the backdrop of the turbulent end of the Tokugawa Period (1600-1868 CE).

Half a year has passed since monsters disappeared from the the tower of Druaga, thanks to Jil and his companions who defeated the evil god Druaga. Jil and Fatina survived the collapse of the tower and tried to live their lives after the betrayal of Neeba and Kaaya. This changed when they rescue a little girl named Kai, who tells Jil to take her to the top of the tower after showing him an unpleasant vision of the future.