Creating Destiny -- it's a longer drama, but it's pretty decent
Dal Ja's Spring -- I adore this drama!
Rent a Girlfriend Home for New Year -- It's a Chinese drama that I didn't enjoy too much, but it fits.
Borrow Your Love-- Yes, there is a fake lovers plot. It's very much unimportant to the plot and barely mentioned. The lead girl is slightly childish. I hesitant to truly recommend it.
I want to recommend Bad Family even though it doesn't exactly fit your specifications. A bunch of strangers pretend to be a fake family. The ones playing the uncle and niece start to have feelings for each other and there is some romance. It's a hilarious drama.