Right off the bat, the drama did a poor job establishing the mysterious M and its mystery. The story was so soulless and shallow it made the 12 episodes runtime so damn dreadful. The whole trio couples were lackluster from all angles, both the actors and their characters. Dialogue was riddled with platitudes and awkward exchanges, making each interaction painful. Even the central mystery, which could have been the saving grace, was handled so clumsily that it failed to generate any suspense or intrigue. The mysterious M could've been an alien for all I care. The ML's sister was the only real sensible semi-functional piece of story in the entire thing. One more thing: from a production standpoint, it adopted the deplorable style of cutting everything short and prematurely; nothing plays in full.