Both dramas' story are set in Unified Silla Dynasty, both main character from both shows are played by the same lead actor and about the same premise, merchant, sea, war. And this show has reference Jang Bo Go the main character of emperor of the sea a few times in emperor Wang gun and also directed by the same director.
both is about the main character's journey to become the King. Since both drama are produced by KBS, the way is tells it's story it's similar. It's also nice to see Kim Yeong Cheol and Kim Gab Soo, playing king and subordinate in both shows before our main character succeed his character as King. The Great King, Sejong mentioned about Goryeo a lot, to learn about the history you can watch Emperor Wang Gun to understand part of the story.
Story about founding of a country, similar premise (mention of Goguryeo), same lead actor playing the lead title character of both shows. Also you will find some of the supporting casts are also both in these shows. If you are interested in history, the country Balhae is also reference/mentioned on emperor Wang gun.
