MAYBE, rather than being a super ultra mega M, what if sayama's actually just an S?
maybe he's doing this to just tease our mc or make her cry. But he doesn't knows that the mc is an alien/has been living under a rock so she wouldn't find anything wrong with this and would just go with the flow.
OR MAYBE, they're both aliens from two diff planets and now are having issues communicating. Big oof.