TBH Mika was smarter than most women. she realized that if a guy could cheat with her then he could cheat on her... I've seen women in real life who fool them into thinking that they are special and the guy who cheated on their partner with them would never cheat on them... delusional... you're right, once a cheater, always a cheater.
Jeezus why were most of the women in this show acting crazy? like the women with "smell fetish" or the blood milk woman... smdh... maybe the short run time didn't provide enough character development but most of the women seemed insane...
The ending was great. The frail tragic Nana we see at the beginning is an illusion. The Nana we see at the ending…
I agree with many of your interpretations but I don't think she decided to marry him b/c she related to his past, I think she decided to marry him b/c he is just a tool for her happiness... like you said she had decided to be happy. it's funny that the two roses in the beginning seems to IMPLY that she killed her stepfather AND her mother and has been manipulating the counsellor and the writer, but if you take the story at its face value she comes across as the victim of her circumstances and she is the innocent doe eyed victim.
Well this turned out to be a total disappointment... I love good ghost tv shows and good BL... you would think a movie that combines both would have been right up my alley but nope this failed in both aspects... Ended up fast forwarding through most of the second half... :/