Time

Jeon So-min was originally offered the lead female role but declined it.

On August 26, 2018, lead actor Kim Jung-hyun dropped out of the cast due to health issues including an eating disorder and sleep disorder; the production team revised the script to have his character naturally exit the story instead of replacing him.

Kim Jung-hyun officially finished filming his scenes on September 3, 2018, after his departure was announced.

The script reading for the series was held on April 28, 2018.

In July 2018, Kim Jung-hyun faced controversy over appearing 'emotionless' during a press conference; his agency explained that his deep immersion into playing a terminally ill character made it difficult for him to maintain his physical and mental condition.

In 2021, Kim Jung-hyun released an apology letter after a tabloid alleged he had requested the removal of several scenes involving physical contact with his then co-star.

Two episodes did not air as scheduled because MBC broadcast the 2018 Asian Games instead, including the South Korea vs Bahrain men's soccer match on August 15 and further Asian Games coverage on August 23.

To make up for the missed episodes, the finale on September 20, 2018 aired four episodes back-to-back starting at 10 PM, covering episodes 29 through 32.