The story is taken from the famous Nordic saga, but is based on the adaption of Richard Wagner: Der Ring des Nibelungen, a cycle of four epic music dramas.
Central element of the story is of course the stunning Ring of the Nibelung, guarded in the depths of the sea by the nymphs of the water. According to the legend, the owner of the ring will get an enormous power that can challenge even the gods.
The hero of the manga is Siegfried, who grew up in the woods with the blacksmith Mime (a dwarf), and is accustomed to harsh life and fighting. He embarks on his destined journey when Mime is killed by a soldier and he is out to get revenge. On his journey he will meet Woden, the god of thunder, and his daughter Brunilde, with whom he falls in love.
(translated from: Shoujo Manga Outline