As the title says.

Who is the mysterious stalker? Why? What clues have we had so far that points to them?

And what are their motives?

Maybe one stalker was someone wanting to protect the FL, while the other was the one who was trying to curse them?

I wanted to create this thread so we can organize our thoughts and theories in a single place for easier access and reference.

Please mark spoilers accordingly and indicate what episode they are from so people can avoid it if they haven't watched that episode yet.

Although the drama has kinda jumped the shark for me (after Ep. 11), I do think that there are two stalkers.

First one:  Jae Kyung - after HJ said : "please will you come" while thinking of Jae Kyung, w/in a few days a man in a black  hoodie followed her (and therefor knew her address) and then JK moved into the bottom floor of her house.  Coincidence?  Maybe - but if so, pretty bad story-telling.

Stalker No. 2 - the Creepy Gardener.