There is no story really to be honest. A grandpa who doesn't look like it falls for a high school girl but Twilight did it better. Perhaps because Pattinson. The casting here was questionable to say the least (apart from the side characters). Episode 1+2 were actually pretty good but then...boredom.

1. There is no chemistry between the leads (FULL STOP). Not to mention the cringy interaction between the overly childish behavior from the FL and the overly fatherly and awkward male lead. The age gap would not have been a problem had there been better acting involved. Actually the FL's approach to her character reminded me of the FL from When I Fly Towards You, only there the chemistry between the leads was 200% solid and the FL's acting spot on. Why this casting here? Did the director order this approach? Just awkward.
2. The bromance works, the side characters and their stories actually succeed in being more interesting than the main story.
3. I am angry because series that deserve first place got overshadowed on dramalist by this mediocre work. And it's not the works fault, they did their best, it's the reviewers fault who are not even trying to be more objective.