The King : Eternal Monarch
더 킹 : 영원의 군주 (original)
A modern-day Korean emperor passes through a mysterious portal and into a parallel world, where he encounters a feisty police detective.
Starring Lee Min-ho, Kim Go-eun, Woo Do-hwan, Kim Kyung-nam, Jung Eun-chae, Lee Jung-jin, Jeon Moo-song, Kim Young-ok, Jeon Bae-soo, Seo Jeong-yeon
Watch "The King : Eternal Monarch" on Netflix released in 2020. It's a drama and sci-fi & fantasy show, and has a rating of 8.1 out of 10 from Imdb which is very high for this kind of show.