Fairly certain this relates to the recent NES Princess Peach Sprite Redraws. The colour pallet in combination with the mushroom commentary can't be a coincidence.
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)?
To the dudes credit, from the only screenshots we can see it's the other girl flirting since she uses heart emojis whilst the dude just writes text or some face emojis.
