I think that the dialogue in Episode 22 between Wol Ryung and Kang Chi hides a lot of what's about to happen!
1st
Wol Ryung told him not to be afraid of what he chose (being a human)
"The moment you lose yourself in fear you will loose everything.The opposite of trust is fear"
So I think Kang Chi will succeed in becoming a human unlike his father who was afraid of being betrayed .It was his heart. His own fear made him into a 1000 year demon. That won't happen with Kang Chi cause he will stay strong and he knows that YW loves him and won't betray him no matter what. He trusts her
2nd
Wol Ryung told him that it's better not to have any resent or revenge. Such feelings are against the laws of nature.Believe in karma.People get what they deserve as they go through life. (That in my opinion means that the bad guy Gwan Woong WON'T die but his fate will be either exiled or imprisoned or something like that)
Now about Yeo-Wool's whole FATE thing about the peach tree and the crescent moon.
Tha Monk told her the first time they met that
1st
He told her
"True Love will find you"
What that means in my opinion is that Kang Chi whom she met as a child and who she loved as a child finally found her after many years.They didn't just meet NOW. They have known each other for many years but just couldn't remember.
So that part of her fate came true in episode 3. True love DID find her indeed.
2nd
He also told her
"A peach tree under the crescent moon. When you meet him THERE, run away"
Who did she meet under the crescent moon????? The BAD GUY who tried to kill her.She met Kang Chi in the forest NOT under the peach tree.They run in order to get away and right at the peach tree the bad guy appeared. So? That's the one whom she met under the peach tree and she should avoid him because one of them will die (according to the Monk).So Kang Chi saved her and that was the moment her FATE changed!!!
AFTER that incident she kept asking the monk what if I can't avoid it because she thinks that the one she met under the moon is KC (and she already developed feelings for him and remembered him from their childhood).So she keeps asking herself "WHY HIM"? . Why did it have to be him!!!!!.
The Monk also later found out it was KC whom YW met under the peach tree (He doesn't know about the BAD guy's appearance) so he figures that these two are the ONES who shouldn't be together and that one of them is going to die.
Both the Monk and YW think KC is the one met under the peach tree!
BUT fate was already avoided and changed for YW at the moment Kang Chi saved her.
Well that's pretty much my thinking about KC being a human and YW's fate and one of them dying.
I could be wrong and none of the above happens or happens somehow differently but you can't blame a person trying to analyse a little bit more.HAHA. Even if I'm totally wrong I hope some of it makes sense!
Just my way of thinking.