Moon Embracing the Sun (2012)

Both dramas involve a man (Kim Soo Hyun) looking for someone who presumably died years ago.

both dramas are adaptation of novels by the same author

=> There is a prophecy in both dramas about "two suns cannot exist in the same sky"
=> Same child actors of the 2 main leads which are Yeo Jin Goo and Kim Yoo Jung (personally I don't ship the two former child actors unlike many but it's still interesting too see that their only scene together in Iljimae is so similar to their first meeting in Moon Embracing the Sun, falling petals also feature in some romantic scenes of them both in both dramas).
=> Two half brothers who are rivals for almost everything, half brother envies the male lead for the attention he has with his parents (or their foster parents in Iljimae), to everything the male lead has compared to the half brother, to the female lead that loves the male lead over the half brother (interestingly, the male lead in both dramas are both the younger half of the two brothers and also also the sons by the legal wife of the dad).
=> Eunchae's good heartedness (female lead in Iljimae) reminds me of Yeon Woo (female lead in Moon Embracing the Sun), this is especially true with the young Yeon Woo (Kim Yoo Jung). Han Hyo Joo and Kim Yoo Jung are so in sync with each other as actresses and are really good in playing these beautiful kind hearted noble girls that every male lead likes. (I personally feel Han Hyo Joo would have really rocked the role of Yeon Woo, Yeon Woo with her memories is especially so similar to Eun Chae).

Both are historical dramas with political intrigue, romance and magic.

The series tells the story of a man-turned-immortal, Bulgasal, who wants revenge from a woman with a mysterious past and present, who he deems responsible for his immortality and miseries from the past 600 years, hoping to free himself from his curse.

kim soo hyun so cool and funny and so smart in this drama all of his film or anything

Whether it be historical or modern days, both stories depict that first love never dies.

I love the casting, they portrayed their roles very well.

Both are darker, more intricate historical dramas with a similar tone and pacing. In both the FL's is originally the king's bride, but circumstances and political scheming result in her leaving the palace/being presumed dead. Eventually years later, she returns to the palace and returns to her position as queen. The ML in both is struggling against powerful people in the palace, all while trying to protect the woman he loves. Both stories have shamans.

Both are romance historical dramas with happy endings. Similar part of plots - evil girl steals identity of the good girl and the main character keeps looking for her.

859 AD. The once-great Tang Dynasty is now declining. Numerous rebel groups have formed, the largest of which is the House of Flying Daggers, based in Feng Tian county. They steal from the rich and give to the poor, gaining the support of people. The local deputies have managed to kill their former leader, but the rebel group only becomes stronger, due to a mysterious new one. Jin and Liu, two police captains, are ordered to kill the new leader within ten days.

Zhu Yan Zhi, disguised as a man, seeks to learn martial arts with an elite clan. Once she begins her intense training, Zhu finds herself at odds with her trainer and superior, Liang.

The reference was in SSL, so it reminded me to finish watching and I am SO SO SO glad that I did! <3

Han Joon Oh is a leading South Korean celebrity. He is stunningly good-looking and tall but is secretly plagued by an inferiority complex that leaves him permanently insecure. One day, he is hired to appear in a public service video. But the shoot goes horribly wrong, and Han Joon Oh is involved in a potentially fatal car collision. He is only saved by the quick thinking of a female firefighter named Kang Young Hwa, who pulls off a heroic rescue.

Han Joon Oh’s representatives hire Kang Young Hwa to work as the star’s personal bodyguard, recognizing her incredible talents. But when Han Joon Oh awakes from his stupor in the hospital, he has changed completely – as his body has now been possessed by the spirit of a nobleman from ancient Korea. This nobleman, named Do Ha, was killed by his beloved wife Han Ri Ta – and the vengeful spirit is on a single-minded quest for retribution…

- ML and FL are separated
- ML does not recognize FL even though she resembles him of somebody special
- ML was ruthless to FL at some point because she resembled him of somebody special
- power struggle
- crown prince / king ML

Both are historical dramas and they were centered around the royal family. They also contained a story in which the king's wife was jealous of the king's love towards another girl. They also had cute and funny, romantic moments.