Mr Sunshine is a very wholesome show. It's one of my all time favourites, even though I'm not a sucker for historical dramas. Even though the plot is very slow, at least in the beginning, you barely feel it because it's very captivating. It is one of the best written dramas and the cinematography is astounding! And trust me, you wouldn't be disappointed by the ending.
As far as romance is concerned, there is a lot of it, and it's beautiful to the core. There are moments where you will feel your heart pound of your chest and melt the next moment. Like I said earlier, it's beautiful. There's no other way to describe it.
You have to give it a shot, and trust me you will not be disappointed. I highly recommend this drama!