In 1909, the famous assassination of Ito Hirobumi was prevented by the appearance of the mysterious figure Inoue Gen. Then human history was rewritten. By 2009, the entire East Asia region became the territory of the Japanese Empire, and Seoul became the third most important city in Japan. The Korean-Japanese "Japanese" Itamoto Masayuki (Jang Dong-gun) is a loyal spy of the Japanese Investigation Bureau. His friend and partner is Saigo Shojiro (Nakamura Toru), and his strong opponent is the underground anti-Japanese organization called "Korea Freedom". "Korea Freedom" created a terrorist attack on the Inoue Art Museum. When Itamoto Masayuki was ordered to investigate, a stone from the Stone Age unearthed in Harbin, China, "Moon Spirit" made him inadvertently discover the great conspiracy hidden by the Japanese Empire for a full hundred years. He chose his life path again, and he and Saigo Shojiro turned from friends to enemies.