How Best to do a Two Way Translation, in Real Time?

I've got a bunch of recommended translation apps – Google, Kulikuli and Deepl are the ones mentioned most often.

What I'm not sure of (and can't find via Search) is how best to run a two-way translation. On previous trips I've used google translate to translate in one direction or another, but had to manually switch direction.

Is there a clever app or way that helps translate two ways?

Or do I need to separate devices, one set to translate Japanese to English and the other English to Japanese, in order to hold a back-and-forth conversation?

Any tips gratefully received.