I really need to write a review about this series.
It's not a bad story and it is entertaining, but the problem is just that if people think about what happened they'll realize that the main characters aren't a smart as they are supposed to be portrayed in the story somehow. I get that the writers wanted to make the story interesting but there is a major problem with it. However, I can only explain the problem in detail if I write about what is happening in one part of the story. Therefore, for the people who like not knowing the story before watching it, they should stop reading here.
So SPOILER from here on.
Everyone who watched it will know what happens but if they had just killed the past self of the evil guy in the scene where they found him after he wrote this apology letter he wouldn't even have had a chance to threaten anyone. If they had killed him nothing would've happened. There wouldn't have been a bomb, the girls' father couldn't have been hurt or killed in the future and the MLs' brother would've never dissappeared or died. None of that could logically be a threat because if the evil guy dies in the past, he wouldn't exist in the future.
It annoyed me so much that the main leads just couldn't understand that, especially since one of them invented the time machine and the other came from the future. They should know better.
And the evil guy talked so much stuff that, to me, didn't sound very smart, I can't understand how the other people in the story were manipulated by him so easily.
This story would've been much better if they had dragged out the search for the evil guy a lot longer or made less episodes, because if they don't find out who he is, they cannot kill him and therefore he can actually threaten them. It would've made so much more sense.
End of SPOILER.
So I agree with some of the reviews here. There is a lot of logic missing in this story. The idea was very interesting and the story could've been amazing if they had concentrated on logic.
Also, this series would've indeed been better if there were less episodes than 16.
So if you like thinking about time and space and can make some sense of it, then either ignore the mistakes in the story or don't watch it, if you get annoyed easily.