this is the show which main genre are not crime and investigation yet  all audience became investigator not leaving a single clue  and those who are roughly watching it without alert for dialogue and crime scene (i mean show screen)  they are confused 

conclusion of show : audience became investigators  LOL 

lets see who can solve this case before 15 episode  

this is what I love the show. it makes you think and pay attention :)

Exactly my thoughts :) It's a really interesting drama. I hope they don't end it like "Black". It was a strange ending.

All of these thoughts are interesting but it keeps making me wonder what is the purpose of yo-yo boy? Why does he want to interfere in the first place? Why is he so fix on TE and LG in the first place if they represent the red string and of fate? Is it a big deal if their fate ends?  Does yo-yo boy have a superior giving him this task to focus on this couple? 

—tbh I think some of the people here on the forums should had been added to the writing team of this drama, their ideas and theories are more logical and intriguing LOL 

Red string has a very important meaning. If you know the Japanese anime "Your Name," you should know why it is so important. Or just read about it, it's from Wikipedia;.              The Red Thread of Fate (simplified Chinese姻缘红线traditional Chinese姻緣紅線pinyinYīnyuán hóngxiàn), also referred to as the Red Thread of Marriage, and other variants, is an East Asian belief originating from Chinese mythology. It is commonly thought of as an invisible red cord around the finger of those that are destined to meet one another in a certain situation as they are "their true love".[1] According to Chinese legend, the deity in charge of "the red thread" is believed to be Yuè Xià Lǎorén (月下老人), often abbreviated to Yuè Lǎo (月老), the old lunar matchmaker god, who is in charge of marriages. In the original Chinese myth, it's tied around both parties' ankles, while in Japanese it's bound from a male's thumb to a female's little finger, and in Korean culture, the red thread is thought to be tied around the little finger of both parties. Although in modern times it's common across all three cultures to depict the thread being tied around the fingers, often the little finger. The color red in Chinese culture symbolises good fortune and is also the color of traditional Chinese weddings where both bride and groom would wear red throughout the entire procession or at some point during the marriage rituals.

Interesting! Thanks for sharing! It’s a waste of yo-yo boy If his only purpose is just to be a matchmaker lol 

Not only. I quote conversations between a boy and Tae Eun in episode 11, when he helped her escape:.                                      B: I warn people of danger and defeat the enemy.                        T: What? By the way you're in this world too (they met in her world, when he collided with her on the street and her pass fell into the canal).                                                                                 B: There's only one of me. I went to the other world. I'm restoring balance. There are too many enemies.                          T: You...What is going on? Who are you?                                          He is definitely a guardian of the balance (or maybe a God). What I'm curious about what is the relationship between him, Luna and Tae Eul, because he talks with them and helps them. Are Luna and Tae Eul the same person? Certainly Luna is not a bad person, because the boy talks with her.

 Izyda:

Not only. I quote conversations between a boy and Tae Eun in episode 11, when he helped her escape:.                                      B: I warn people of danger and defeat the enemy.                        T: What? By the way you're in this world too (they met in her world, when he collided with her on the street and her pass fell into the canal).                                                                                 B: There's only one of me. I went to the other world. I'm restoring balance. There are too many enemies.                          T: You...What is going on? Who are you?                                             He is definitely a guardian of the balance. What I'm curious about what is the relationship between him, Luna and Tae Eul, because he talks with them and helps them. Are Luna and Tae Eul the same person? Certainly Luna is not a bad person, because the boy talks with her.

Thanks! Very interesting! I agree, I’m curious about his relationships with them too! —I suppose you could argue fundamentally no one is a good or a bad person and that everyone is gray. Luna and TE can’t be the same person because Luna is planning to steal TE life after learning of it from Lee Rim. Luna told yo-yo boy she’s about to do something that deserves punishment. Yo-yo boy also talked to lee rim as well. 

I think the real question is why tf did Luna kiss Shin Jae ( `ε´ )

Jk lol

All these assumptions seem pretty legit but where did the Lady Noh being the lover of his grandfather come from? Did I miss anything? 

Lady Noh is from Korea. Probably Lee Gon's grandfather brought her in. The first clue was a volume of poems that she knew from Korea: Lee Gon recited one of the poem to Tae Eul. She knew an author, because he is from her world. Lee Gon, as far as I remember, bought and took this book to the Kingdom of Corea. Probably he guesses that court Lady Noh is from Korea. In the last episode, Lady Noh asked Tae Eul what happened to the war that broke out in 1950. In the Kingdom of Corea, this war did not take place because North and South are united.                                                                  There is a possibility that court Lady Noh could be a mother of Lee Lim (as we know he is an illegitimate son). But I hope she isn't.

Regarding the connection between Lady Noh and the book, in episode 3, when Lee Gon and Tae-eul were in the bamboo forest, she asked him again what his name was and he said she can't say it even if he told her, and she asked if he is the poet Kim So Wol. When he asked who Kim So Wol was, she remarked how good he was at pretending then  said she won't "finish the last words I had in my heart". This line is in Kim So Wol's poem Invocation of the Dead. Lee Gon brought a copy of the book Azaleas containing this poem to Corea. Lady Noh saw it in his coat, probably recognized the author as from her native world and has been reading the poems since. I won't be surprised if she knew the author personally. I've been wondering if the poem portends a bad ending but hoping not.

Amazing memory! I should check it out before I wrote about it :) I don't know why people say it's boring. So many interesting things can be learned but you have to remember them :)

Exactly! It's far from boring because one has to pay attention to scenes and dialogues that may seem irrelevant at the time but actually are important later on. 

It’s interesting where there are mysteries to consider and contemplate but it’s boring how the show executes and translate them on screen and dialogue is dry. The show entertains new things each episode without really developing things and it’s characters. For example, Did episode 12 need 30 minutes of showcasing the romance? No, it could had been used to develop other characters and subplots, But it’s just my opinion lol 

I think that they sacrificed so much time for romance, because viewers accused them of showing not enough attention to the feelings of the main characters.