I was transported to another world and defeated the Demon King, but I can't go on with my companions who don't know about "miso soup"

I was transported to another world and defeated the Demon King. That part went fine, but I just can't understand why my companions don't know what miso soup is. Despite the fact that Earth terminology has been working perfectly fine until now? Besides, these guys are using Earth terms themselves. For example──. ※This work is a participating entry for "Radio Award 3". ※This work is also posted on "Alphapolis".