The plot seems a little tacky and clumsy at first when there wasn't enough background info (intended; yet didn't do a good job to secure the audiences' attention and understanding) and the way Pisaeng developed affection for Kawi was too easy (but that's how love works). Despite that, from around episode 4 onwards, the plot made total sense and was very logical (if the audiences are logical and empathetic enough to undersand the writing). It became real, sympatheticable and understandable.
I especially love how the series targeted multiple points of philosophy and humanitarianism. It was just right (not overdone), impactful and digestable. I was given a chance to look at multiple new aspects of life through the writing. Also, the couple's progress through friendship and love was so interesting and so cute. They actually built a realistic and believable love progress, no big gestures, no going out of boundaries and I absolutely respect that because love stories in real life aren't majestic.
However, the only plot hole I find to be brain-itching is the time traveling of Pisaeng. On episode 12, He traveled back to the day he first turned the globe in Kawi's room when they had just received acceptance from Pisaeng's mom. So on his first try with the globe, where did he go ? What did he experience ? How did he feel ? Did he affect anything in the past and the future ? So...that took down a point.
Despite all that, i praise the two main actors heavily ! They kept it real and made it lively. I fell in love with the chemistry between them and cried for them when they fell apart. The two really delivered a prominent yet dilemmatic love.
All in all, this series will probably not be the best of this year but will definitely feed your soul well so i recommend you watching it.