Based on the theory of parallel universes where there is a constitutional monarchy ruling the (parallel) nation, a political plot to the assassinate the king takes place.

 

The coup is thwarted by the sudden appearance of a unknown person, who saves the life of the young heir to the throne, but drops a policewoman's ID tag on the scene.

The killer then escapes to another world, using a piece of a stolen mystical half flute like artifact. 

Years later, still obsessed with finding the identity of his mysterious savior, the young prince now king discovers the portal to the other world, crosses over, and finds the person who's ID he found on that unfortunate night.

Kingdom of Corea, Winter of 1994 Lee Lim and his gang of rebels enter the palace to kill the King ; Lee Lim's brother.

They kill him and Lee Lim picks up a mystical artifact which is mentioned in the synopsis Manpasikjeok which looks like a flute. 

In the midst of all this Lee Lims son Lee Gon around 12 years old walks in the room and sees his father is dead. 

Lee Gon the assasin tries to kill the child prince but soon someone who's masked walks in and starts firing bullets and saves the young crown prince but drops an ID card of a policewoman; while Lee Lim escapes with half of the flute, that then opens a door to the parallel universe i.e Republic of Korea. 

As Lee Gon is next in line for king he is crowned as king the next day and meets jo yeong also around the same age as him and we find out later that he becomes the bodyguard.

Republic of Korea Winter of 1994; Lee Lim has now escaped from Kingdom of Corea after killing his brother the former king.

When he lands in this universe he meets his brother from this universe and goes ahead and kills him, the person who is him in this universe is paralyzed he kills him too and he dumps the dead body of his look alike in Kingdom of Corea so people might think hes dead.

The uncle of Lee Gon who is a doctor in Kingdom of Corea gives a false statement to stop the chaos in the country that Lee Lim is dead even though the body that turned up looked like Lee Lims but the dna was different.

He finds out about Lee Gon of this universe and kills the child too. He lets Lee Gons mother live (Lee Gons mother in Kingdom of Corea had died long ago) who he plans to use later as an example and reveal about the two universes to People of Corea and take down the king in process and rule in his place. Though the main motive Lee Lim wants the flute is to become immortal.

Fast forward to 2019 Kingdom of Corea now has a constitutional monarchy. New characters are introduced. 

Prime minister Go seo ryung, Bodyguard Jo yeong, A Photographer turned member of PR team of the royal family.

Lee Gon still is looking for the person in the ID card but since its from another universe he doesn't find anyone. Soon he sees a person in a rabbit hoodie and follows them and lands in a similar place that we saw Lee Lim land and since Lee Gon had half of Manpasikjeok the door to the parallel opens to him too and he crosses over to Republic of Korea and meets her.

Republic of Korea 2019 shows us the person in the ID card is Jeong Tae eul who is a police officer.

We also see more characters like Kang shin jae and Jo eun sop two of them are look-a-like of the ones we saw in Kingdom of Corea.

Lee Lim for 25 years has been building an army, he offers people a chance for better life with a condition that they have to kill their counterparts and take their place.

Now to bring balance back to the world Lee Gon and the good people start their work.

Time Travel. Lee Gon time travels along with Jo Yeong back to the assassination night and things change a bit.

This time Lee Lim gets the entire Manpasikjeok and the half that Lee Gon has disappears in his hand and the the other half that the future Lee Lim had(which now Jeong Tae Eul took from him) disappears too.

Lee Gon kills Lee Lim and in the place called the middle Tae Eul shoots the future Lee Lim. So now Lee Gon has the entire Manpasikjeok.  

Shin jae is actually from Kingdom of Corea and was brought by Lee Lim when he was a child.

The Shin jae of Republic of Korea had met with an accident which had put him in a coma and therefore since then he was in a coma (only his father knew about this as he made a deal with Lee Lim years ago)

Yo-yo kid that we've seen before, morphs into a young man who claims the door will close but the memories will remain. 

We see more flashes of yo-yo kid at various ages in the kingdom and the republic.

Turns out HE IS THE MANPASIKJEOK. Now he contemplates whether the memories should remain or not and as we see more of the story; turns out he decided to let them keep their memories.

Lee Rim’s body disintegrates in the between place, and Tae-eul comes to an understanding that Lee Gon succeeded but cries when she assumes he can’t return.

Now since everything becomes balanced all the things that were changed because of traveling back and forth go back to before we see that in 1994, the scar on Gon’s neck disappears.

In the republic, Shin-jae disappears from a group photo.

While Jeong Tae Eul and Lee Gon remember each other others don't with the exception of Jo yeong.

Now with the entire power of Manpasikjeok in his hands as promised before once Lee Gon opens doors to all universes trying to find Jeong Tae eul. Finally they meet and hes surprised to see she remembers him.

They get back together!! Aww can you imagine that kind of love where your lover travels to all the universes to find you! XD

The rest of the characters got a happy ending too. Nari and Eun sop are married and luna and shin jae are at the start of a romance story. Jo yeong and counterpart of nari have started dating. Lee gon and tae Eul travel back-and-forth every now and then and more in love than ever!!! Yayy happy ending!

 

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