The only one who did know is the author, the rest of us are all clueless as to what the heck is going on. Maybe he went to meet with him, maybe he went to attend that guy's funeral. The story of the dog seems to be an explanation why Hyunwoo did not take the relationship further, because he doesn't want to experience feeling loss again. However, what's in the phone? Is Hyunwoo still alive? Is he conscious? Is he on life support? Does he remember? ... there are many questions that can be asked and only one person may possibly have the answers. I will not rate this series until I finish reading it, as I am too confused at this point to do so.
The Only One Who Didn't Know