Gonna be quick here, because there is not much to it.

Its a decent plot, short episodes (maybe 40 minutes of actual runtime), doesnt overstay its welcome.
The plot is very simple, though wouldnt call the show secret romance since before it fully starts people already know about it, nothing new here, rich boy meets poor hard working girl and teases her on the job then they date.
As far as acting goes, from what i have seen of him this is one of Sung Hoons better roles, though still feels kinda stiff. Song Ji Eun plays a very cutesy, maybe a bit ditzy hard working girl and she played it pretty well.
There is also typical chairman dad trying to set up his son with a girl that is super into the son and has some "status"
Most of the side characters are pretty underdeveloped, but they fill their stereotypical roles.

Honestly 7 might a bit much for the show, but there wasnt anything i straight up disliked, just nothing much out of the ordinary.