Wow. I'm actually surprised at how dense Paisen is. He told her to draw her favourite animal, and she drew him. YOU ARE HER FAVOURITE THING AND SHE BASICALLY CONFESSED TO YOU, YOU FOOL!
I guess he did kind of realize for a little bit when he thought back to what Prez said about love, but then he immediately dispelled that thought for some reason. Looks like Nanashi is going for the long haul with this.
Unlike a lot of other manga like this there is constant, steady progress. Especially with Paisen. He's getting more assertive and confident, albeit slowly. His denseness, and denial, about Nagatoro's obvious feelings for him (even Gamo and co., or at least Gamo, have noticed her feelings for Paisen) is getting slightly annoying tho.
With that said, Nagatoro was great this chapter. I say that, but she's great every chapter. That transition from smiling to dead serious angry was great. They were right to be fearful. Invoke Nagatoro's wrath, especially when it comes to her gross (beloved) senpai, and you won't have long to live.
Also, did anyone else notice that when Nagatoro confronted the thot couple Nagatoro's hair is reversed? On page 3, her hair is hanging down on her left and her hairpins are on her right, but on page 4 it's reversed. First time I see Nanashi make a mistake like that.