This show had everything: the sad backstories that make us empathize with the characters, beautiful redeeming arcs for the 2nd generation, as well as some amazing high school friend group scenes! Absolute must-watch for anyone wanting to relive their high school days.
When I initially started watching this, I thought it was a similar concept to a Bollywood movie from 2010 called Action Replayy since it involves the son going into his parents' past to make them fall in love. But as the episodes went on and Choi Se Kyeong's character was shown more (+her and Ha Eun Gyeol's relationship developed), it reminded me of A Map Of Tiny Perfect Things because of the similarities in the main characters stuck in the same "time loop" and needing to help each other to get back to the present. If you liked this drama, I highly recommend these two movies!
The last episode was probably my most favourite, seeing the positive implications of the changes that happened due to the time-travel instead of things going bad because of what was changed.