Best rom in a non-romance genre

I've seen a few dramas which didn't have the romance tag, yet somehow was 10 times better than than any rom drama. Like some chinese or hong kong drama I watched where the FL was the ML's  bodyguard and neither of the was simple but had had the best romance that trumped any romance tagged drama I watched. Don't remember it's name, though :/ But their romance wasn't really in focus or the goal of the drama,