Doraemon: Nobita and the Birth of Japan

Doraemon and his friends use a time machine to travel back to ancient Japan, where they encounter a young boy named Kukuru. Kukuru explains that his tribe has been captured and enslaved by a hostile group led by a figure called Gigazombie. Moved by Kukuru's story, Doraemon and his friends decide to assist him in freeing his people and restoring their freedom.