I'm not sure why you want the 32U4 to read the keypresses from the laptop's keyboard? One reason that I can think of is to have led indicators that e.g. indicate capslock but you might have other reasons in which case I'm curious about them.
The solution depends on the operating system. One possible solution (the only one I can think of at this moment) is that you intercept any key press at the operating system level and send that to the 32U4 over e.g. serial; you will have to write a PC application for that.
It was not quite clear to me. Now it is.
Fair enough; I thought that you were indicating that you couldn't physically connect a keyboard.