In the wilderness of Hokkaido, the Ainu people of Japan live in harmony with nature. Kotan Nakamura is a young Ainu boy living peacefully until he meets a tiger one day. This tiger, Dan, has escaped from a train that was carrying him to a zoo. Together, they discover mysterious ruins hidden underneath the ground.<br /><br />Within the ruins, Kotan and Dan discover an old man named Upopo living there. He tells the boy and the tiger about three keys to a fantastic treasure. As it so happens, the evil Sekkoku Kou is also searching for the treasure and shoots Upopo. Before he dies, Upopo gives one of the keys to Kotan.<br /><br />Now, Kotan and Dan find themselves involved in an ugly battle as numerous villains track them down to try to get the three keys so they can claim the treasure.