Considering the world they're in, would being a teasing tsundere w/o the toxicity even work considering i'd imagine there'd be more 'competition' (altho i guess it's just the chastity reverse as opposed to the ratio also being like 20 girls to 1 guy in a class) even tho mc's gonna have a reputation as a 'slut' doesn't mean there wouldn't be other guys easy to deal with even if they don't act like mc lol
Yeah he'd just be the tsundere childhood friend. Low-level teasing, but always sticking around the person they like. And like you said, it's a sex inverted world, with no other added on "men are incredibly rare" settings. So just flip the sexes, and you have a mesugaki osananajimi character. Those can "win" if they have scenes where they lose control and accidentally say what they really mean, and of course, not being so toxic as to have already turned the MC off of them entirely in the first place. Nagatoro (post rewrite) is a story that exists, and they get together in the end. And that's like nearing the toxicity threshold that I have.
THIS bitch had already planned out the mental and societal degradation of the "MC", to the point of using even their own friend against them, to break them down to the point of desperation. That's FAR BEYOND standard tsundere.