Love this drama.
I think it could be better if some loose ends were addressed, but that is ok.

STORY - wonderful idea with lots of possible endings. Could be used for other dramas

CASTING - The women were amazing. Shin also

SOUNDTRACK was very good

ENDING - could be better but is was ok

REWATCH - certainly, even knowing the end.

OVERALL - I Wish I could see more dramas with this starting idea!
A must see for people who like interesting plots and mystery!