Given that the uncertainty of Mizuki's gender and their inability to come out, I think it still reflects a lot of trans and non-binary people in unaccepting society and environment (I am not trans or non-binary, just my thought).
as others have pointed out: there's some interesting implications to the fact that Kikyou is clearly worried about Kasuza eating the cake + Serika eating pre-packaged food instead of the cake... did Kayoko lace it with something (or, at the very least, do they think she did)?
