The last chapters are a flashback to how Geumsun and San met.
They explain that San was actually a human that could see ghost, goblins, reapers, etc. Hwan did to him the same thing he did to Eunjae (kill the people that surrounded him) to then possess him and eat him, Geumsun realized that and tried to kill Hwan while he was in San's body (since the myth says that's the only way to kill a ghostly monster), but apparently he couldn't do it (we saw him trembling while holding the sword) and Hwan got away injured. That's why they have history together and why Hwan hates Geumsun so much! ヾ(❀╹◡╹)ﾉ~
Ohhh, thank you so muchhh!!!
Im sorry can someone explain what has been happening on the latest chapters? Im a bit confused, english isnt my main language （/TДT)/