The c-dramascape is well populated by crime/thriller/suspense dramas. However, if you throw in a sci-fi spin to the mix then the candidates for top dramas in this genre is somewhat thin on the ground. Maybe it has to do with censorship or culture but the writing in that sub-genre tends to be more muted and less innovative than creators from beyond their border. I’m glad to report that this show stood head and shoulder above the typical competition.

It is not a spoiler to tell you that the story is revolve around our protagonists being “trapped” on a bus that will explode and kill them in a matter of minutes. Each time they die, the sequence resets (hence the title) and they return to the bus. This is all laid out in the opening scenes and reinforced in the first episode. As our leads live through more cycles, they learnt how to work with the time loop and manipulate the events. They have to find out why they are looping and do what they can to stop it.
As this is such a suspenseful drama, I shall try to remain spoiler free. Most of the comments will be intentionally vague.

As you can imagine, with the scenes and scenarios being replayed over and over again, the writer have to find ways to present their predicament from different angles and perspectives. This is where the writer did a very good job for much of the show.
Similarly, the actors are repeating variations of the same plot, but they showed a lot of emotions and dedication. The leads were standouts and kudos to them. There are definitely no squeamish or wimpy characters here.

The production value of the show is quite good. Maybe it is the repetitive nature of some scenes that allowed them to get more bang for their bucks by editing explosions and car chases shot from different angles to generate more “unique” footages. One thing that piqued my interest is the police station. It seemed to be modern and “nice”. I don't know if it is based on a real police station or whether it was embellished.

I appreciate the show expending efforts to fresh out the backstories of some support roles. It made their behaviour more meaningful.

Alas, I wish the show was able to sustain this high standard all the way, but it did begin to falter towards the end. Not so much individual acting and scenes but the consistency of the main plot.

A lot of the issues came from the time loop concept. By the time we find out who the bomber is, the rest of the story is not that hard to deduce. Even so, the repetition still went on when the leads failed to break out of the loop. This gave us a lot of time to contemplate the raison d'être of the main event. It exposes some narrative weakness, and you start to question the goals and motivations of the antagonists. The internal logic still holds, but there are now cracks where there was none before.

The Show also paid a lot of attention to the backstory of the antagonists. It was nicely done and with a delicate touch. However, by then we have already sat through several backstories, we know what will happen and when, we know who did it so there is little intrigue left. This only brought about a distinct change in pacing and tension.

Another issue is why the leads are involved? They were just trapped and then released once they solved the puzzle. These issues would have been less contentious if this was a two hours movie or have fewer episodes.

The ending also did not sit well with some viewers (no spoilers). I can sense the writer was preparing us for a different ending, but it took a detour. Was it because of censorship?

In the end, rating this show is like judging some Olympic sports. You start with a perfect 10 and then you start to deduct little bit here and there as you spot minor imperfections.

OST was fine. Rewatch is difficult as there is no mystery left and the repetitions will test most people's patience.