Nothing really happened. They are together, have a dog, Mountain God wanished without a word to some other city, Yoo Na is getting merried to Woo Taek. So...like I said, nothing really happened.
I agree with the Mountain God part... No grovelling, no excuses no nothing... That made it a very bitter pill…
If its a first kiss with that person she turns into a dog one minute after the kiss and after that every night on midnight for 100 days. She thought it was the first kiss with Seowon so she ran.