Hmm...
The male lead in
Boss & Me is tough and cold publicly, but he falls in love with the female lead very soon, and doesn't try to hide that he's in love.The contrast is really sweet. She's a very nice and cute yet insecure character.
I think this may be more of a personal thing because a lot of people didn't enjoy this drama, but I always loved the male lead in
ToGetHer because he treated the female lead very differently: despite his usual loud and arrogant self, with her he's more quiet and considerate. She was the only one he would show his vulnerability to, but he also helps her and protects her as much as he can. The female lead is very shy, but also quite dependable and rational.
Sorry, I can't think of anything else for now... I think
the forum question I just posted could be kind of similar to yours -- and the male lead I mention there from
Lady & Liar may fit, I don't know -- perhaps someone will suggest a drama to me that will have the type of character you're looking for!
Good luck :)