The story of "The Quest for the Lost Kingdom" is not a specific Japanese folktale or story. However, there are many Japanese myths and legends that involve quests and lost kingdoms, such as the story of the legendary hero Yamato Takeru who searched for the lost land of the gods. In this story, Yamato Takeru travels through treacherous mountains and forests, fighting off beasts and evil spirits, to seek out the lost land of the gods known as Yomi. He meets the ruler of Yomi, the god Izanagi, who warns him to leave, but Yamato Takeru refuses to leave empty-handed and demands the sword Kusanagi, one of the three sacred treasures of Japan. Izanagi agrees, and Yamato Takeru returns to his own land victorious.