the previous posters are right. there could only be 2 possible scenarios to explain this:
1. Murakami was still up doing "who-knows-what"
2. Murakami was asleep, but she feels it whenever Moritani stops time!
.... oh there's a 3rd one..
May be she just woke-up in the middle of the night, wanting to pee, or drink milk... and her pet cat was roused, and then the cat stopped. haha. I cant imagine her KNOWING without seeing other people/things stopping.
Unless, we go back to point number 2, where she feels it! :)
cant wait for what's gonna happen next!