Mama (2014)

Han Seung-hee is a successful painter and a happy single mother to her son, Geu-roo. But when she gets diagnosed with a terminal illness, Seung-hee becomes determined that Geu-roo will be adopted by a nice family after she's gone. So she seeks out her ex-boyfriend Moon Tae-joo, and ends up befriending Tae-joo's wife, Seo Ji-eun. Meanwhile, a much younger photographer Gu Ji-sub falls for Seung-hee.