I actually really liked this drama. At first I didn't really like the FL but that's because we saw the drama from the ML's perspective. Once he finally really sees the FL in the past and present, with the ML as an adult, beyond his crush on her, her character becomes so much more understandable. I also LOVED that the ML and FL always liked each other, it wasn't just the ML pining after the FL for 10 years. If you look closely, the "wedding ring" she's wearing at the start, is the ring the ML bought her for his confession, something that was later confirmed. The only thing I hated about this drama was that the FL took so long to get together with the ML because she was always running.

Despite the fact that I felt bad for young Kang Shin Woo because Ji Soo fell for the adult version of him, I LOVED that the present (2017) plot had older Kang Shin Woo be Ji Soo's first love, though it was confirmed that Ji Soo fell for all three version of Shin Woo (originally timeline young Shin Woo, older Shin Woo and alternate timeline young Shin Woo). I still had second lead syndrome of sorts for young, alternate timeline Shin Woo, because he always came second to Ji Soo after the older version of him. He never knew what it felt like for have his (young) love to be reciprocated as it was for the original timeline Shin Woo (AKA older Shin Woo when he was a teen).

Also, despite the fact that Shin Woo couldn't change his own future by going to the past, I loved that he was able to change his fate, he was able to change his present (his future from the point the drama started at). He was also able to change the future of his old class mate, preventing his death and allowing him to have a bright future ahead.

Unlike many other time travel dramas I've seen, this is the only one that had an ending that made sense of sorts. We got to see the original (older) Kang Shin Woo (the ML) get his happy ending by going back in time, figuring everything out, and then changing his present. And we also got to see young Kang Shin Woo (the SML) grow to become the older version of himself (the SML becoming the ML) that meets Ji Soo in 10 years, with several time jumps showing him aging and finally meeting Ji Soo at the time he was meant to. Both leads, though the same person, got their HEA in a way that made sense to the timeline of events, entirely because the SML made it a point to follow the ML's footsteps.