Story:
Time-traveling was well done. The rules of time-traveling were explained in every episode and made us not confused with the flow each time we enter a new ep. For a 20-min./ep drama, this was an easy watch, but at the same time, it feels too short since we're always getting cliffhangers at the end of each ep and stressing also because of the conflicts which were well-executed. I have seen people creating their own theories while watching this drama, yet some of the scenes were beyond expectations. This drama is a fantasy-thriller one. So I have fewer expectations on the romance side between the MC. The FC is smart, but she also made reckless decisions (out of her emotions) which was a reality when we were put in the same situation. Overall, this is really fun to watch and will make you think of so many possibilities during their time travel.

Acting:
Acting was good. I can't say it was the best, but it wasn't bad either. The leads were improving and satisfied my expectations until the end. Their chemistry was on-point and overflowing (even without a kiss scene). Yeri pulled out Harin's bubbly character well and Hongseok made Seojun's emotional scenes effective. But I really want to appreciate Hyemin and Sinu's portrayal! These characters added flavor to the tension of every scene they were in.

Music:
The 2021 versions of the OSTs were on point! Both of the 2 songs were released 10 years ago and it was well-planned along with the storyline. On Rainy Days showed us Harin's POV while Even Days showed us Seojun's. I really love how it was also inserted in the emotional scenes (particularly in the flashback scenes). However, I felt like there was excessive use of some BG music which I think is unnecessary in particular scenes.

Rewatch Value:
I'd love to rewatch this whenever I don't feel like watching new series.

Kudos to Yeri and Hongseok and all other casts and staff for creating this masterpiece!
If there would be Season 2, I'm hoping this will still be directed by the same PD.