How to close Gap in an “open” bedroom?

Ideas to close the gap between kitchen and bedroom. (Upper right of picture). I think the width of the ledge is only about 6” or even less. Want to minimize light and sound. Apartment, so nothing super permanent. But I’m not too afraid of some screw holes.

Ideas to close the gap between kitchen and bedroom. (Upper right of picture). I think the width of the ledge is only about 6” or even less. Want to minimize light and sound. Apartment, so nothing super permanent. But I’m not too afraid of some screw holes.