This drama serves as evidence that grandiose scenes, big names, magnificent costumes, and outstanding OST are not essential. Instead, the only thing you need is a genuinely touching and marvelous story brought to life by capable actors, proving the timeless truth behind the old saying 'less is more'.

Story: 10.0 *** THE SPOILERS AHEAD ***
A truly beautiful and highly unique story, presented in a manner distinct from any others I've encountered so far. Despite its moments of profound sadness, it remains incredibly touching, especially approaching the end, at the end of the 13th episode I've felt that deep emotion of sadness when you are about to lose someone, when you are aware that you're not going to see that person anymore, the one you love so much but you can't do anything about it, they did an excellent job of bringing it to the screen.
The last episode attempts to console the audience, but in my opinion, they didn't even need to do it. The understanding, the love between them, I already sensed that deeply, and if the drama had ended at the 13th episode, it would have been enough, at least for me.

Acting: 9.5
Overall acting is good enough and with excellent job of main leads I give it 9.5, especially the main actress, she is the star of this drama, if you re-watch the episode with his first time travel and their last meeting, you can see her caring love for him and sadness intertwined, just great.
*** THE END OF THE SPOILERS ***

Music: 9.0
It's very good, maybe my rating is a bit high but because of overall impression, I must give it 9.0

Re-watch: 10.0
Constructed in this manner, it leaves ample room for exploring this amazing story through multiple viewings, perhaps even in a non-linear order, and being such a wonderfully written love story, the re-watching value of this one is through the roof.

Conclusion:
My ratings here are purely based on the love story, other things are not so important in this case, maybe some people will find a lot of problematic things with the plot, and maybe they are right, but I ignored all possible time traveling issues and everything that comes with it, only thing that matters here is the love story between them.

So if you enjoy love story and romance without all the unnecessary drama (misunderstandings, love triangles etc.) in it but told in very unusual and unique way, then I highly recommend it.