Scarlet Heart: Ryeo It was released in 2016 and starred Lee-Joon Gi as Prince Wang So and Lee-Ji Eun as Go Ha-jin.

When a total solar eclipse occurs, a woman from the 21st century, Go Ha-jin, returns to the Goryeo Dynasty. He wakes up in the body of a 16-year-old teenage girl named Hae-soo. There, she fell in love with the 8th prince Wang Wook (Kang Ha-neul) and then the 4th prince Wang So (Lee Joon-gi), who hid his face behind a mask and earned the nickname "wolf dog", making people afraid of it. Love, rivalry, politics, and friendship that occur between handsome princes fighting for the throne, friendship, and love

Totally worth watching! 

There’s Baekhyun from EXO too, his character on this drama was so silly.