At first, I was thinking this chapter would somehow shoehorn Kai's mouth into a beast's breasts. Instead, it's a side character arc that involves former antagonists in a story that happens at the same time as the endless school arc. Filler or not, I am totally up for some side character development. Just a shame that it doesn't involve one of the initial soldiers Kai worked with, like the beast guy (Ren? Something like that). I don't even remember the catgirl's role in the story though, but who cares; she's cute.
Also, the dimorphism for beasts is surprisingly not that huge. Men are humans with animal ears, tails, horns if applicable, and blunt noses. Females are the same, but with normal noses. TECHNICALLY lazy since it's still "Human, but...", but at least it's not the usual nonsense of men looking like monsters while women are generic anime girls. I mean, they are, but still!