Somewhere in the MMORPG called "The World," a group is gathered at a pub, awaiting the start of an event. There, old friends and acquaintances are reunited, including those who rarely log on. Some are even forging new relationships for the first time. Together, invited by the hacker Helba, the group leaves for the event in the Net Slums where a celebration awaits them all. [Written by MAL Rewrite]

In 2029, a large scale ground sinkage occurred in the Mediterranean Sea. Chemical elements such as oxygen, carbon, gold, molybdenum, and cobalt disappeared from the earth's crust suddenly. The human population was decreased by 90% in sixty years. Researchers found out that the disappeared elements were drained into a planet "Nega Earth", located in another dimension. To save the Earth, a special team called the "Element Hunters" is organized. All of the members are under 13 years old, because young and flexible brains are needed to access "Nega Earth".

Yumekui Merry begins with Yumeji Fujiwara, a seemingly average high school student. But ten years ago, Yumeji gained the ability to see the dream auras of other people around him. This ability allows Yumeji to predict what type of dreams people are likely to have next. The dreams of others may not be a mystery to Yumeji, but his own dreams have recently left him puzzled. In dream after dream, Yumeji has been pursued by an army of cats lead by John Doe, who claims he needs Yumeji's body to enter the real world. These strange occurrences get stranger when Yumeji meets Nightmare Merry, a dream demon seeking to return to her own world. Using his powers, Yumeji decides to assist Merry in getting back home. But Merry's very presence in the real world means that the barrier separating dreams and reality has been broken, and not all of the dream demons intend to come to Earth peacefully...

Twenty years prior to the story's beginning, an asteroid headed for Earth destroys Pluto. Due to Pluto's destruction, the asteroid, which is dubbed Thanatos, becomes temporarily stagnant. Now, in order to avoid Earth's impending destruction, the International Solarsystem Development Agency (ISDA) works on the "D-Project", and creates the "Dragonaut" after finding a dragon egg under the ocean. This weapon's primary purpose is to destroy the asteroid when the time comes. However, they soon find out that the asteroid is not their only threat, as powerful dragon-like creatures, which are bent on destruction, appear on Earth. After witnessing a murder by one of the creatures, Jin Kamishina, a lonely 18-year-old boy who lost his family in a shuttle accident two years ago, gets involved in the mysteries of the dragons and becomes the chosen pilot of the Dragonaut. Helping him on his journey is Toa, a mysterious girl who saves him from falling to his death after the creature attacks him. As they get deeper into the mysteries of the dragons, they encounter new friends and enemies, and also begin to develop a closer relationship. (Source: Wikipedia)