Lee Bo-young and Ji Sung met in Save the Last Dance for Me (she's the second lead, though) in 2004, got married in 2013
Han Ga-in and Yeon Jung-hoon met in Yellow Handkerchief (they're supporting characters, not leads) in 2003, got married in 2005
Song Yoon-ah and Seol Kyung-gu acted together twice--in the movies Jail Breakers in 2002 and Lost in Love in 2006--and they got married in 2009
Maeda Atsuko and Katsuji Ryo acted together in Dokonjo Gaeru in 2015, got married in 2018
Eikura Nana and Kaku Kento met in N no Tame ni in 2014, got married in 2016
Bonus: Yamaguchi Momoe and Miura Tomokazu met in the set of Izu no Odoriko in 1974, made a string of movies together, and have been married for forty years; she left show business when she married him, though