I've heard the following exchange between two characters, where B agrees to do something dangerous that she previously was dead-set against but chooses to do so now of her own volition:
B:「構いません…」 <pauses for a couple of seconds, then looks even more decided>
If it were just simple emphasis, B could just have repeated the first form with two different vocal/facial expressions, but the fact that there are two distinct forms of 構う makes me think that there's a fundamental subtext that I'm missing, other than one being a more "polite" form. Can someone enlighten me?
EDIT: Added some more context, though I'm not sure how much is enough. B is ヴィヴィ, and A is マツモト, from Episode 3 of ヴィヴィ -フローライトアイズソング-, around 7:45 (hopefully the timestamp is consistent between streaming platforms).
She generally uses a respectful tone, is very mindful of others, and almost always uses polite forms e.g. 〜ます, as well as expressions like させて頂きます / auxilliary verbs like おります that I associate with polite speech (is that 敬語?). The switch to a less formal expression is very sudden and coincides with a big decision on her part.