The story and screenplay combined with the consistency in character development portrayed by awe-inspiring acting by most of the major showrunners created this tear-jerking (sometimes) drama with a boat-load of romance.
The chemistry between the main leads is one of the slam-dunks of the show. The zeal to follow one's love no matter the circumstances is quite well-written. The transition between episodes is fluid enough to not cause a distraction or end-up in major plot holes.
Although the drama hit many home rums with respect to relationships overall, nonetheless we find a lack of gradual sibling bonding between the male lead and his sister. The final arc of the season, especially the last 2 episodes show major sibling bonding.... which is closer to a real-life scenario..... which is kinda welcome.
Like most romance dramas, the existence of cliched misunderstandings and sacrifices is present, but not to the point of being a hindrance to the overall flow of the story. All-in-all, this is a refreshing portrayal of pain, love, regrets, memories and all of them being the reasons to live.