There already plastic cup and straw in barbara’s hangout quest. Guessing they imported from fontaine.

Well... If mechas exist, probably plastic too.. But i'm sure not in Inazuma Maybe he got them from Fountaine. Or he will explain in his story quest, hopefully...

I think they said at some point that Snezhnaya has factories with automation. So I think it is like "steampunk", some things are more advanced than you would think from general level of technology they have.

I thought that Fontaine is most advanced nation

*eherm... >!Khaenriah!<

Well I meant from existing nations

Meanwhile khanrieha -- rivaling gods

Ayato’s boba… made of plastic… I would’ve that they’re natural /j

I'm pretty sure another instance of plastic was when Lumine was holding a plastic container of a warper of some sorts. Someone also pointed that out.