Responses
I went back and reread this (like, twice now?). I don't think he did, either. I was even realizing she may not have even stayed the night. He didn't know what she looked like, just her shoes and they were really basic women's dress shoes, so even though he saw a woman the next morning, that might not have been her.
Thinking it through, I think it's possible Sagara actually came home (and brought his assistant) to finish up work there so he could be home for Aoi, rather than making him wait another night.
(Still not cool telling him his mother didn't want him though. That pissed me off.)
I actually don't think that he slept w her. He prob only let her stay over to see aoi's reaction or smth. It just doesn't fit his character. At least that's what I'm going to believe