Well, truth to be said, as much deluded and depraved as he is, hes was really planning on asking her to marry him, so at least he wanted to take some kind of responsability instead of having her as a sort of a mistress
Sorry, it’s a bit long…
Well, what I’m about to say is just speculation, but it would fit the personality of that MF principal.
He doesn’t want to take responsibility or truly love Maria Akeboshi, Mari Nagare, or Mari Akeboshi. He just wants to possess her. That would align with his selfish character, and he could boast about having Maria all to himself.
Marriyng out of love is what Taiichirou and Mari did, but we can’t say that the principal loves Mari/Maria the same way Taiichirou does.
He says something like (if the translation is accurate) “Maria is obedient and does what she’s told even if her face shows she doesn’t want to.” Like, we’ve all been in love, and we don’t even have to talk about love—just think of someone we care about, like our parents or friends. We don’t make them do things they dislike while concluding that if they agree, it means they’re masochistic.
All this to say that the principal doesn’t love Maria at all, and his proposal isn’t honorable but rather a form of subjugation. That’s why he goes completely crazy to the point of bleeding when he sees Maria genuinely open up and show a “happy”/consenting face—without disgust—something he’s never seen from her before… with a man she’s not supposed to know.
