The whole thing was so heartwarming and beautiful. It was aggressive when needed, and extremely realistic in every way except for the magic time travelling part. Everyone's lives, experiences and feelings were explained and well represented, and i felt that nobody was left behind.
The four main actors did an amazing job, they're so good. I loved that they were completely different and unique in their own way. The way it's written! Omg, i loved that we can see the parents in many different scenarios, how they are there for each other when things were tough in adulthood, how they met and fell in love, and how they continued to love each other when their lives were better financially and socially in the end. We don't usually get to see these many dimensions in a couple's relationships in series. I loved seeing them grow up together.
The only thing is that i wish the ending was a bit longer, and we could see how On Eun Yu's life changed too, and how her's and eun gyeol's relationship was now that they got back, her dinamic with his family and all.