This is pretty common for English to be a bit broken for foreign characters in manga like this. It has a kind of charm to it I think.

For those curious, the changes I’d make for more natural English are because of the following reasons:

• It feels a bit creepy to me to address a stranger (especially a little girl) so casually with “Hello pretty girl!” - To me, “little” feels nicer, and probably more in line with the original intent.
• I get the impression the speaker probably was originally trying to find out what the girl (Osaka) was doing, and less about asking how she was doing.
• I think the last sentence was trying to ask about her “cosplay”, and that probably got muddied in the translation from Japanese to English. We do sometimes use the word coplay, but not for everything, and I don’t think (especially given the year this was released) some English-speaking adult would use this term - “dressed up as” sounds more natural and era/situation-appropriate.

Again, broken English. Here’s why I’d make this change:

• It’s obvious he thinks that maybe the costume has to do with a Japanese religion, and he thinks he might have misunderstood the situation.
• I don’t really understand “I mean…” we usually use that if we’re explaining something and trying to make our point more understood. That doesn’t seem to be the case here, though. So I interpreted that as like “I’m still trying to understand”, so more simply “I wonder”.

Side comment: I love Osaka’s face remaining static in these last two cells. Truly she is processing a million thoughts a second here (and none of them are related to the current situation).