It's safe to say now, back in chapter 3, Kasumi's hairclip got hidden on the locker because of the bullying.
Also interesting to note Kasumi calls that the 2nd time she and Michi spoke, while back then Michi said she'd never spoken to anyone yet. That might come up again.
And Sayaka commenting on all the creepy people around lately means either she just got her powers recently, which kind of explains why she hasn't figured it out, or something's calling ghosts to school.
Quite some setup for a side chapter. And I'm all for a cute side couple.
But I do hope Honami focuses on trying to find out why it looked like senpai saw her, which will probably happen when Micchi and senpai talk (probably because of the Kasumi's feeling left out in class again issue). How will Kurotori pretend she has no idea the gay ghost of an idol is walking with her every time she's at school?
Since Aizawa knows for sure Sayaka can see her, I'm sure she'll want her help fixing this. Sayaka will ask why she isn't talking. Michi's head will explode.
I really figured Sayaka would be the mentor figure, since supernatural stories generally come in 2 varieties: a) the protagonist is experienced or b) they're learning from someone experienced. With her being Michi's opposite (can't identify ghosts and always calls them out) they're going to crash headfirst soon.
And there's not much reason to keep pretending she can't see Aizawa when Sayaka proves ghosts don't always attack. Not to mention that half-body ghost in the shed seemed to be going after the mark on Michi's neck, which means she's literally got a target painted on her regardless.
Dorothy said upcoming chapters would focus on 3 things: Kasumi's subplot, the connection between Michi and Aizawa, and the mysteries of Aizawa's death. I wonder if we're going to start touching on those last 2 this volume; we're about halfway.
Either way it's a good sign when a manga shifts focus to side characters early. It means it's comfortable going for a longer serialization.