*flashback to 106 years ago*

Kaesong city, Goryeo Dynasty, in 1910.

"Wife, i got this invitation from the royale Im family in Kaijo." Minatozaki Nobu told his wife one day. 

(Kaijō is what the Japanese used to call Kaesong city with in 1910-1945 during the Japanese occupation.)

"Oh, Im family as in the parliamentarian?"

"Yes, they invited us, our family to visit their house in Kaijo and stay in there for several days. Seulong said he wants to treat us as his way to thank me for the result of our agreement. So what do you think? Should we go?"

"I think declining his invitation will be somewhat rude, especially his family is a noble one. But my concern will be about our children. I don't think leaving them in Nippon while the two of us go there will be a good idea. Especially after the last attack we got. I'm afraid if they know you're leaving, and our two daughters are staying unguarded, they might use this chance to take a revenge on you."

"You're right. Then let's bring Momo and Sana as well to Kaijo. Leaving school for a week, i don't think that will cause a big problem, not when our two daughter are smart kids just like me."

"Oh Heaven, you and i both know that they got the brain and beauty from me." Mrs. Minatozaki playfully flaunted.

"Hahahaha, fine then. I won't ever win against you. Now please call Momo and Sana. We should tell them about our little voyage."

*****

(In Kaesong, the royal Im residence)

"Oh, konnichiwa." Im Seulong and his wife greeted their guest who came from a far place from theirs with a bow.

"Oh, annyeonghasimnikka." Nobu and his wife greeted back and also bent their body to bow. It's such a beautiful sight to see. The two families who came from different country seemed to respect each other despite the 'not-so-good' relationship shared between the two countries at the moment.

"Seulong-ssi, this is my wife, Tori and these two cuties are my daughter, Momo and Sana." Nobu proudly introducing his family to his friend.

"Ah, nice to meet you all. And let me introduce mine too. This is my wife, Miyoung."

"Where is your daughter, Seulong-ssi?"

"Ah, my Minyoungie is still sleeping in her room. Miyoung-ah, go wake her up. I want her to meet Nobu-san's family. She must be happy for having two new friends too."

"Ne, yobo." Miyoung replied and excused herself to wake her daugther up.

"Momo, Sana, how old are you? You two seem in the same age with my daughter." Seulong said as he looked at the two beautiful teens in front of him with a smile that caused his eyes to vanished.

"Hajimemae, watashi wa Momo desu. Yoroshiku onegaishimasu. I'm 17 years old this year. And my sister, Sana, she'll soon turn into 16 next month." Momo as the older one among the two stepped forward to properly introduce herself and also her sister who seem to be a bit shy and timid compare to her sister.

"Ah, then you two will be my Miyoungie's unnie then. Minyoungie is 15 years old now. She just celebrated her birthday few days ago." Seulong said.

"Unnie? What is unnie, Momo oneesan?" Sana cutely asked to her sister who seems puzzled, can't answer her either since Momo also not sure what 'unnie' means. It's also her first time to hear that word. Seeing the cute confused girls in front of him, Seulong just let out a hearty laugh as he patted the two girl's head in fatherly manner while Nobu and his wife also smiled along seeing the warm interaction that Seulong made with their daughters.

"Unnie means 'oneesan'. Since my Minyoungie is younger than Momo-chan and Sana-chan, she will call you two with 'unnie', a word that we used in here to call someone that older than you when both of them are girls." Seulong explained. "Wakarimasu ka? (do you get it now?)" 

"Haii." The two young girls answered in unison with a firm nod.

"Abeoji (father), annyeonghasimnikka." Hearing that cute feminine voice, all of the people in the room automatically turned their head toward the source of that voice, only to find a very pretty young lady with very fair skin and wearing a light blue hanbok walking gracefully toward them.

"Ah, Minyoung-ah. Here, this ahjussi is abeoji's chingu. His name is Nobu samchon(uncle), and his wife named Tori imo-nim(aunt). And these two pretty girls are their daugters who will be your friend now, Momo unnie and Sana unnie."

"A-annyeonghasimnika, Nobu samchon, Tori imo-nim, Momo unnie, Sana unnie." Minyoung timidly greet her father's guests with a deep bow.

Momo and Sana can't help but admiring this beauty in front of them. Momo is not trying to be subtle at all by eyeing Minyoung with such adoration in her eyes as she's smiling widely at the latter who can't even look at their eyes for more than 2 seconds. Sana too can't stop herself from get attracted toward the girl. But unlike her sister, Sana can only bites her lower lip to prevent herself fro