The Holy War between Celestial Clan and Archfiend Clan ended. But they all fell into the world of men, Midgard. Now, the Celestial Clan plans to return to the Heavenly Realm as well as the Archfiend Clan to take revenge on the Great Creator. What will happen to the people along with the Celestial and Archfiend? A young boy named Lucian, who dreams of becoming a Holy Knight, inspired by his father, who is also a Holy Knight, experiences an unexpected journey. While he and his little fairy friend Alette are on Mount Iris, they find a strange portal in the mountain's dungeon. Lucian and Alette are sucked into the mysterious portal and end up in the underground world, Fallen Realm. What fate awaits them? What revelations will they discover on their unexpected journey?