As a fan of science fiction movies and shows and from those that I've seen, this may not be my number one but fortunately one of the best. A parallel universe story with various twists. It felt like I was watching FLASH that needs to go back to the past to change the timeline, and near the end was like LEGEND OF THE BLUE SEA that waited for a long time to come back and suddenly just arrived at home.
If you are looking for a simple love story or a plain science fiction, this one is not for you. This is like a brain game. Every single detail shouldn't be missed, well, of course, there are some scenes and dialogues that are so cheezy and quite long, but that's the downside of the story.
The writer was not able to justify bringing the two lovers in one world, but that's the exact reality of what might happen if there is really a parallel world. I love the story.