Just caught up with this one last night, and it might even beat out the Harmageddon episode as my favorite so far. It was just wonderful - happy and sad and charming and bittersweet and chaotic and touching and, when all's said and done, contentedly optimistic..
And Yachiyo got her body back.
Her reaction when she first learned of the engagement was telling, though nobody really pointed it out. That was an emotional outburst at the thought of losing Ponko. I think she's a lot more human than anyone realizes.
My current theory is that the author and his assistants (or maybe just his assistants and he quit bothering long ago) have a great big die with story tropes on each face and as necessary, they just roll the die and do whatever it says.
Since they finished the "sports festival arc," they had ro roll the die again, and it came up "study group."
And here we are.