Taken from OneMang: Twenty years before the start of the history, the asteroid, heading towards the Earth, destroys Pluto. Due to the destruction of Pluto asteroid, which is called Tanatos, is temporarily stuck in the Pluto orbit. Now, in order to prevent the inevitable destruction of the Earth, the International Agency for the Development of Solar Systems (ISDA) works on the "project D" and secretly creates a weapon called "Dragons" after the decoration of the Dragon Eggs under the ocean. However, they soon discover that asteroid is not the only threat of their threat, because the powerful and destructive Dragons of Tanatos appear on Earth.