Coffee Prince: Due to her tomboyish appearance, the male lead mistakenly believes the female lead is a guy. She ends up working at his coffee shop - where only good looking men are hired - and they gradually become very good friends before they fall in love.
Bromance: Although there may be early hints of attraction, the focus of the drama initially is building a solid foundation of friendship. The female lead has been forced by her parents to pretend to be male until she turns twenty-five so the (presumably straight) male lead doesn't really think of her as a romantic option for a good while. The attraction isn't immediate on her end either. The female lead is pretty unassuming and straightforward (aside from having to keep her true gender hidden).
Ever Night: This might qualify? The main characters are not related but they've lived together most of their lives; as a young child, the male lead took her in when he found her as a baby. There are subtle hints of attraction in the early episodes, but they're subtle enough, I guess, that many viewers didn't pick up on it and ended up pretty shocked by the transition to a romantic relationship (much) later. Their dynamic in the earlier episodes has more of a "best friends" or "siblings" vibe overall, and the female lead is definitely a simple girl (in a good way).
