Responses
I think Jean poisoned Rafa, who always protected Eda from predators, so he could come back and do this without Rafa being in the way.
Rafa basically kicked Jean out after intense arguments with each other, possibly because Rafa could tell Jean wanted Eda.
Jean has practice using herbs for medical purposes. He could easily have taken Rafa out of commission so he could go after Eda.
We expect Jean to be the culprit based on the current chapters, but if the author decides to twist it into something... well, like other twisted manhwas then there is a possibility of that fake sleeping priest is the culprit.