I think there’s kind of a lot going on here. Like, Rei automatically defaults to the idea that Usagi is blaming them when she talks about the bus disappearing, basically totally reversing her rather amicable greeting. Which on some level tells us a lot; she actively doesn’t trust that anybody is actually going to be on her side- the police don’t seem to be, other people are blaming her, and she doesn’t feel like she really has anyone to turn to except her grandfather, and he’s the one everybody is blaming.
Like, Rei never communicates any idea that she is being blamed, or at the very least that she cares about that. What she cares about is that her grandfather is being slandered and that isn’t something that she’s inclined to stand for because to her, her grandfather is basically all she has.
Meanwhile Usagi is just kind of confused as to the idea that Rei or her family could even be responsible for what happened. Like she’s a cute girl and she was pretty nice to her and that slots her as a Good Person in Usagi’s mind, and of course a good person would never do anything like that! Usagi just is somebody that really trusts people and tries to focus on the good in them, and that’s definitely one of her best qualities.
And she doesn’t try to get into a fight with Rei, but immediately apologetically backs down and just tries to explain herself; like, on some level she does get that Rei is tired of being accused and just wants to communicate that she wants to help.
And Usagi kind of lays it all on the table- that she trusts Rei, that she thinks she’s a good person, and really she just wants to be friends. She barely knows Rei, but she knows her just well enough to have faith that she’s the kind of person Usagi thinks would be a good friend (see: almost everyone). But Rei is just so tired and closed off at this point from literally everyone, it feels like, turning against her, that she just isn’t interested in what Usagi has to say.
And Usagi respects that. She backs off, and says that she’ll come back tomorrow, it’s a sharp contrast to their constant fighting in future episodes, but an understandable one. On some level Usagi seems to understand that Rei is upset and she can sympathize with that, and knows that getting into a shouting match isn’t going to actually accomplish anything; and it’s quite plausible she’s just a little bit intimidated and an argument sounds a little scary.
Like, it’s a good scene where you can really sympathize with both of them and really touches on where the two are at at this point, hitting on some of Rei’s issues and some of Usagi’s strengths.
