Basically, from what I could surmise and hypothesize:
- Sato is academically-poor, a given, but not dumb as bricks. He might as well be as dense as one though.
- Todome has the mad hots for childhood friend Sato, to the point that she doesn't mind repeating a year just to be with him
- Todome is either:
- a genuine ⑨-tier airhead, or
- a Kaguya-sama tier of reverse-psychology warfare genius, pretending to be a ⑨-tier airhead
But the manzai style employed in this manga obscures the accuracy of my observations above, so it'd be wise to halt myself from over-analyzing a comedy manga.