Kirishima is planning something big, a big clean up of rivals maybe.
Let's remember, the Somei Grandad did ask him to take care of Yoshino, my guess is, this is one lure bait plan kirishima is doing, and that's why he got close to Nao again, to use her in his plan, to lure the insects he's going to crush.
I'm excited to see the rest hahaha