Thanks for the new chapter!
I personally have seen cases like this while I was in high school where a girl seems to be kind and sincere for some time to a boy (a friend of mine since primary school) then discovering that the girl is talking shit about said boy, and even said she can make him carry his bag and stuff if she wants to (i.e. make him her lackey; has him under her whims). Fortunately the guy learned of this pretty early and started avoiding this girl and just moved on.
Well my friend just brushed it off because he is not interested in the girl anyway but I guess, for Shizuki, it really had a subjective impact on him and triggered him to change for the better; and fortunately he didn't necessarily become an edgier person. But yeah, there are really mean girls out there, and there are really weak boys so 'results may vary'.
Now we have to know how Kusunoki's personality changed when she entered middle school.
Also other than that, I think it is okay if Kusunoki still wants to be friends with Hebikawa, but I hope Hebikawa will not do exploitative stunts to her just to make her "show her true colors"; it seems that this is how Hebikawa likes to run things on people she is interested in. If things go wrong with Kusunoki, she might make Kusunoki hide back into her shell again, and discourage her from opening up to people again.