Betty

Similarities:
--MCs are newbies/underdogs in the Outsiders/Spirealm world
--Blood, death and dark themes (Spi is darker than IAN)
--Multiple Second Main Characters
--Concealed Romance

Similarities:
--Enemies to Lovers
--Murdery Vibes
--Characters pushed to their breaking point
--Recognizing and owning your mistakes

Despite belonging to different genres (Mistery and Supernatural versus Romance and Life), both series rely heavily on:
--Youth
--Economic and Societal Struggles
--Chinese Culture and Traditions
--Personal Breakthrough

Both Dramas revolve around seemingly mediocre teens that develop a special talent: 1st in Go and the 2nd in Caligraphy (both being one of the Chinese Ancient Four Arts). During their journey they learn about life, friends and family.

Both of these K-dramas revolve around women who choose to enter sex-related industries.
Throughout the series, the main characters encounter significant struggles, primarily due to the societal taboos around sex. As they confront them, they rediscover themselves and get stronger.

Both series tell the ups and downs in love and life of a group of male friends.
Both series are centered in Romance, Comedy and a Slice of life.