Yoon Sang-hyeon knew about Lim Se-mi's death but didn't say anything.
On the latest episode of the KBS 2TV drama "The Perfect Wife", Koo Jeong-hee (Yoon Sang-hyeon) was visited by Lee Eun-hee (Jo Yeo-jung).
Lee Eun-hee got a call by the police and told Koo Jeong-hee that Jeong Na-mi (Lim Se-mi) was dead. Koo Jeong-hee asked if she did it and she told him it was an accident.
Koo Jeong-hee tried to call the police but Eun-hee said, "Do you think you'll be alright if you turn me in? If something happens to me, that's the end for you too. Do you want to be broken again?"