[solatic]

As an American ex-pat (different country, different language, same shit) - 100% prioritize Japanese fluency. It really will unlock doors for you to speak the native language well, it will reduce your sense of social isolation and eventually make you happier.

Seeing other ex-pats here without fluency, their lives are so much more difficult. Not quite as isolating for them, since there's a fairly large English-speaking expat community here, but still, seeing them struggle with the most basic things has given me newfound appreciation for the difficulties that immigrants to the US face while their English skills are weak.