故事发生在某个晴朗的下午，鲁鲁修与娜娜莉一起度过着安稳的时间。突然，娜娜莉向鲁鲁修请求：“想再听以前在皇宫的庭院哥哥讲的那些充满快乐的故事”。为了满足自己珍爱的妹妹的希望，于是鲁鲁修对《CODE GEASS》系列的登场人物使用GEASS的力量。“鲁鲁修・V・不列颠尼亚命令，《CODE GEASS》的角色们啊，成为我所讲故事的登场人物吧，使我最爱的妹妹娜娜莉高兴！”就这样开始了《CODE GEASS》历史上最大规模的GEASS浪费，新的不思议之国的故事就此上演。

It is the second year of the Kowa Period. The world has unified around the reorganize United Federation of Nations, and has enjoyed days of continuing peace, but now, that peace suddenly comes to an end. Suzaku, while travelling as the masked man "Zero" accompanying Nunnally on her visit to the refugee camp, is defeated by a mysterious Knightmare Frame, and the two of them are taken away. Following secret orders from Schneizel, Kallen, Lloyd and Sayoko infiltrate Zilkistan, the Land of Warriors, where they are attacked by a mysterious Geass user. There in Zilkhstan is a person named C.C., known to the assailants as the "former master". In the indomitable kingdom which once conquered even the great army of the Holy Britannian Empire, what do the people desire? Hope, or despair? The people of Zilkhstan Palace certainly know of Geass. What are they, and C.C., planning?