Circle - Season 1 Episode 11 Is That You, Woo Jin?
Overview: The person coming down the stairs turned out to be Woo Jin’s clone. At first, Joon Hyeok denies that he’s Woo Jin because of the real Woo Jin who died. But as the clone tells him his memory of the day he disappeared, he apologizes. He says he’s sorry for letting him go there alone.