What do you looks like? That has been the case without any subtlety since the very start that he's only acting like a tsundere because of his crush.
Tsunderes can be curt and prickly but they shouldn't be outright abusive with no redeeming qualities. Like if they had shown that he said mean things but was also helpful to her or he blushed and looked rattled before he lashes out with some comment to cover his nerves, that's not great but at least on point for the trope. Here he does
nothing but show up and berate her, basically calling her a freak when she's done nothing to him and barely interacts with him. And it's like
poof this is all supposed to be water under the bridge because he's taller than her now and the "natural order" is restored and he can admit he likes her.
That's weak and frustrating. Good tsunderes have to earn their place by showing some softness immediately so that you know they have a softer side and have to grow properly with the potential relationship. Miruporon is a fricking angel and didn't deserve how deeply he appeared to hurt her when she's literally done nothing to him except exist.
I feared this was where things were headed from the beginning, butI had hoped that maybe they would have her stand up to him and tell him to knock it off and maybe that would earn her some respect in his eyes. But nope, we're really gonna treat this like elementary school kids pulling hair and calling names on the playground.