I have a theory but I have to tell you a big spoiler. Are you sure you want to hear it?
As you could see he was sitting and in the bg there’s a family who lost a member because of what they’re wearing. When kang min wanted to call solhee and make up w her he immediately heard the crying family noise and decided not to call her, cuz he had cancer and didn’t want to make her cry at the time he dies.