"Sin (42) and Kim (25) started dating two months ago", their management agency said in a press release on Wednesday.
Despite a 17-year age gap, the two became romantically involved after getting together with fellow actors at a scuba-diving gathering.
Sin has appeared in several hit films after making his debut in 1998. His new movie "DETOUR" hits local theaters this week.
Kim debuted with a controversial role in the 2012 film "A Muse", which is about an affair between a poet in his 70s and a teenage school girl and has built her acting career since then.
She is currently preparing for a TV soap on cable channel tvN scheduled to be aired later this year.
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