Gurus in the late Goryeo dynasty try to obtain a fabled, holy sword, and humans in 2022 hunt down an alien prisoner that is locked in a human's body. The two parties cross paths when a time-traveling portal opens up.

Ean has a critical mission to return to the future to save everyone. However, she becomes trapped in the distant past while trying to prevent the escape of alien prisoners who are locked up in the bodies of humans. Meanwhile, Muruk, who helps Ean escape various predicaments, is unnerved when he begins sensing the presence of a strange being in his body. Traveling through the centuries, they are trying to prevent the explosion of the haava.