Quietly, Usagi thinks of this time in her life as the empty period.
She's always realized that she isn't an independent person, but it takes those few weeks without him to realize just how much she leans on people. More to the point, how much she leaned on him. She relied on him as Tuxedo Kamen to come rescue her when she was in need of it, but she also relied on him to be walking behind her as Chiba Mamoru every day. She might have hated the teasing and felt small underneath his eyes, but their whole relationship became something of a routine. It even felt weird on a day she didn't see him because of how much she'd come to expect his voice call out at the worst possible moment. "Yo, Odango Atama!"
It isn't the same now. Yes, he still teases her, but she can tell there's something different about it. It's something in his eyes that isn't there anymore, a void she doesn't know how to fill and one he doesn't even know exists. It's like he's there, but he isn't entirely there. She has no idea how to explain it at all properly, so the one time she said as much to Rei, she was told to stop being silly.
And maybe she's right about all of this being silliness, but Usagi doesn't think so. How could she when seeing him every day and knowing who he used to be might be gone forever? She doesn't want him back; she needs him. She needs dark cloth and blood red roses and a voice like red wine. She needs him back in her life - all of him back in her life - in any capacity. What she has right now is only part of who Mamoru was, and no turban bound substitute is ever going to take his place. It's only going to serve as temporary distraction. A drop of water when she needs an ocean's worth.
But she can't say that to anyone. She can't explain how it feels like something's missing - like an empty chair that ought to be filled. So, she doesn't say anything and quietly thinks of it as her empty period.
And she waits for him to fill the space.