An extraordinary drama tangled in time

Someday or one day was an amazing drama with an unique plot which tangled in time. The drama's mystery keeps viewers blank about the unpredictable plot and twists. The production team layed down this complex plot to an amazing masterpiece with no loopholes. While when I could predict most of the plot in other dramas I found the story unwinding in the very lasts of the episodes. The OSTs has a lost and at the same time enchanting feeling elevating me. A once in a lifetime drama you should never miss out if your into time travel and doppelgangers.