I know that there are lot of manga with this genre, but I'm looking for one when the girl isn't discovered in the first vol (like all I read).
ex: Some like Hana Kimi if
Spoiler (mouse over to view)
Mizuki would be with Shuichi,
or as Cute x Guy Spoiler (mouse over to view)
Mitsuru discover at the end that Sumi is that boy...
So... a romance manga with gender bending, wen the gender-bending character isn't discovered that fast by the character that she will go out.