1. Will Jung So Min be a part of part 2?
Yes, but only for a cameo.
2. Why is Jang Uk using Naksu's sword?
I’m pretty sure Jang Uk knows that Naksu’s “running wild moment” isn’t exactly her doing and that someone is behind that tragic incident. Jang Uk is probably using Naksu’s sword to look for some clues as to who might be behind her untimely death aside of course from remembering her.
3. Who rescued Mu Deok?
As shown in episode 2, it was Master Lee who helped Lady Jin recover MD/BY’s body. I’m just a bit disappointed that Master Lee did not bother to tell Jang Uk the truth (that Naksu is actually still alive).
4. How does Go Yoon Jung appear again when her body was burned?
Master Lee said that because Naksu’s soul has taken over BY/MD’s body, her real physical traits are coming out.
5. And any other wild theories are always welcomed
No wild theory or whatsoever, I just really want Jang Uk and Naksu to live happily ever after coz they deserve a good ending after everything they’ve been through.