Urashima, much like its name implies, is located very far away from Tokyo and Mainland Japan. One day though, a strange, naked man washes up on a beach. His name is Setsuna. He has no memories, and one by one, he comes into contact with the three daughters of the three main families of the island, Rinne, Karen, and Sara. Rinne, however, is special in that she stays secluded in her house during the day for fear that a rare disease, Soot Blight Syndrome, will kill her. Setsuna tries to understand the mysteries behind this island.

Shichisei no Subaru tells the story of a very powerful party named Subaru in an MMORPG called Union. They travel, have fun, and explore dungeons all while leveling up. However, when a character dies while playing the game, all remaining friends drift apart. Years later, they all are convinced to log into a new game called Reunion. When our main character Haruto does, he explores a dungeon. In said dungeon, he finds a box and when he opens it, the old party member of Subaru who is supposed to be dead is inside, alive and well.