[Masumi, for once, is quiet, picking her words carefully as she goes about explaining just how long she's known about this.]

...A while. He never told me anything until the night before the faire, when I found him about to turn back, but I've had suspicions for pretty much the entire time I've been back in Japan.

[That's going to need some explanation on how she came to those suspicions, since that's not something most people jump to without very good reason, but unfortunately she's still hesitant to talk about why she has this knowledge.]