Hoverlab, a South Korean news commentary site on YouTube, claimed that the actor and the late actress Kim Sae-ron had been in a six-year relationship since she was 15 years old.

Kim Sae Ron and Kim Soo Hyun have been in headlines for their alleged relationship when the actress Kim Sae Ron was a minor and the actor Kim Soo Hyun was 27 years old. These headlines started since the actress Kim Sae Ron was found dead at her residence on Kim Soo Hyun's birthday and the pictures of them circulating all over the internet.

On Feb. 16, 2025, Korean actress Kim Sae Ron was found dead at home. The death of the 24-year-old, who had risen to popularity as a child actress, was later ruled a suicide. Reports soon began to emerge that Sae Ron had owed 700 million won (S$652,000) to her former agency, Gold Medalist, at the time of her death.