In Great Britain of another world, the life of Grand Magi Merlin is nearing its end. Resigned to his impending demise, he passed a book of prophecy written in a foreign tongue to his disciple, Lina. The title of the tome was “The Legend of King Arthur”. Meanwhile, Raito, a Japanese high schooler who adores the Legend of King Arthur, travels to England for a school trip. Raito, who always wondered, “Is there ever a Legend about King Arthur that doesn’t end in tragedy?”, found a strange saga about King Arthur in used-bookshop. But, when he hurries back to his accommodation and open the book, he was suddenly transported to a mysterious forest somewhere—!?