I have friends who learned japanese quite easily. Granted, they where living in japan so that’s way easier being deep into easy practice and daily exposure.

But grammar is quite easy, as well as phonetics (that actually depends on your mother language, for us it is at least).

Of course don’t learn the traditional symbols, or don’t learn how to write it at all, since that would be useless to your goal. If that is even possible I don’t know.

Disclaimer: I didn’t study japanese