so, Kanon's sister gives us an interesting bit of information on lipreading, that at least in her experience paying that much attention to someone while they talk makes you better at realizing what their true intentions may be.
What if this is also true of Kanon, what if she has an inkling on Saki feelings about her, because she too can use lipreading to get to the heart of the matter (in this case Saki's). I don't know if this chapter is setting up foreshadowing or if I'm reading too much into it but I don't think Kanon is entirely clueless about the fact that Saki is in love with her.