I was skimming through the pages (again... for the nth times ) and I found this specific post.
I've wanted to talk about this topic since ages ago; but always found myself neglecting it (for the lack of words, short in thought.....); but now I finally decided to speak my mind.
So, the flower in discussion here is the buckwheat flower.
Like above, I couldn't find the meaning "Lover" of buckwheat flower mentioned anywhere (other than quotation from this drama). As herbs and greens could have different meanings in different countries and cultures, and since I don't speak Korean, I couldn't found references in Korean regarding this matter; all I did was searching at google in English; so I can't be 100% sure that my thoughts are right.
The common meanings of buckwheat flower that I could find (throgh googling) are protection and wealth. Food made of buckwheat is really healthy and that's how it is also called "food for the heart", as it helps to protect against heart disease.
The annual buckwheat flower festival is also held in first half of September, usually from 9 - 13 Sept yearly....
Connecting to our drama, Euntak was born during this festival time; and I think there's reason why writer chose this specific month to be her birthday (other than she and her mom were saved by dokkaebi in February and she should be born 7 months later) - you can trace back to the Reaper first deceased case and Reaper-Goblin first encounter to verify my point.
Back to the buckwheat flower's meaning - protection, the meaning links to our drama in its own official title : GUARDIAN
For him who protects, for him who guards, also it's him who loves!
Some posters already linked Kim Shin himself as lover in the buckwheat flower's meaning in this drama universe. And when he gave her the buckwheat flower at that causeway, it symbolizes him giving himself to her.