A good theory
funny cause yea the way geumsun looked at 704 the « first time » they met each other... looked like they knew each other in the past- like ex lovers maybe
i remember geumsun talking about how he only knew one other human who was so greatly connected w their soul/body and that person is long gone… ever since then i’ve thought it was 704
Someone mentioned the bow belongs to 704 so maybe he will get hurt while using it ,i don't know, we will see
Here is my theory ,Geumsun didn't erase the memories of Eunjae because he has experienced it how devastating it can be to see the one you love can't remember anything while looking you in the eyes with 704 (i still don't know what kind of relation they had but they will surely show us in next chapters) also the other thing is when Geumsun said 'fate is not on my side, not even once' i think he will die while protecting San or 704. The fate has already been decided ,704 escaped from the place he was captivated with a bow and came to Geumsun's place,Geumsun will take the bow and will use it, while using it he most probably will get heart. All the things that happened starting from the San's family history until this point is to determine the destiny of Geumsun(it seems like Eunjae or San is the main character but no it's Geumsun) , what needs to be happen is already happened and i think Yama also knows what will happen in the end and shaped the conditions for this path that's why 'fate makes no mistakes