Vanishing Twin (2000)

Yu-jin is very excited at the news of her sister's returning home. Her sister, Seung-jin, is supposed to come with her husband, Jin-ho. However, Jin-ho tells Yu-jin that Seung-jin committed suicide. Jin-ho seduces the upset Yu-jin, and Yu-jin's husband suspects that Yu-jin and Jin-ho have an affair. But Yu-jin cannot believe that her sister is dead. Yu-jin meets a man who has the same email ID ad her sister.