In the year 2022, a Robot Guard manages alien prisoners trapped inside human brains. Raising the young girl Ean on Earth, he lives in the guise of a human being. One day, when an alien prisoner escapes, the entire planet is thrown into jeopardy and Guard goes back to the past with Ean to trap the alien there. Meanwhile 630 years earlier during the Goryeo Dynasty, an older Ean is known as "The Girl Who Shoots Thunder". While Ean is trying to retrieve the Divine Blade, the key to traveling through time, Muruk, a hapless dosa (Korean tao magician), is aiming to claim the enormous bounty placed on it.