Responses

Plus this isn’t “the second couple's story” the author has said countless times that this story has FOUR main characters. So, no one is taking attention from no one.
The story started with the feeling of responsibility Geumsung had for protecting Yoonwi (704) and the prophecy that the four of them were the ones who would end Hwan
Y’all need to go back and read this story again.
Yoonwi is 704. Euneon is the past self of Eunjae
And Hooseoung is the ancestor of San. The only one who live in this era and is present in the contemporary time is Geumsung and 704 who lost all his memories once he was taken in by Yama and made a reaper. This story is the past. Is how everything started and explains why Geumsung has acted the way he has and why he has such a stormy relationship with 704. 704 as a human, as Yoonwi was extremely fond of Geumsung. It’s implicit that he loved Geumsung. But once a human becomes a reaper they get rid of all human emotions. So, even though 704 feels drawn to Geumsung, he doesn’t know what happened before he became a reaper. This story is Geumsung telling him how it all started and what actually happened between them.