I have seen people rate this 10 and I agree with them if it's only the story of Ha Yi Chan and Yoon Cheong Ah. Their story was perfect for me. But there was no other story apart from theirs.

There was a part where they introduced On Eun Yu's friend's death, but there was no follow-up on that. And the future, I was so curious about how things will end up for Choi Se Kyung, but the only ending we saw was of Ha Eun Gyul's family. Choi Se Kyung, being one of the main characters in the drama, and her ending wasn't even shown.

So yeah, the drama was perfect in the time traveling era, but the future and ending wasn't enough for me.