I'm sorry. Not to be rude, but haven't we discussed this before?
These are language exchange events, not dating hookup events. Why would you be assuming that the girls there are looking for a serious relationship rather than for language exchange, which is the stated purpose of the events?
I mean, I'm not going to attack you for wanting a "particular Japanese partner" (although one could argue that your approach and attitude towards this is counterproductive at best), but if that's your goal, you should probably stick to dating apps and whatnot, where you can at least be assured that the other parties are also looking for the same thing you are.
But the answer to your question is: of course. If you don't actually care about language exchange, then you should probably stop going to language exchange events and wasting other people's time.