depends! At this point, direct focused studies aren't common (i like using duolingo and a free anki card app for that) but I'm always practicing as my job requires constantly working w japanese and learning more
to add: what I do is research obscure anime merch and things related to that, most of which has very little to no english info. deepl (translator that has a handful of languages) and jisho (online jp dictionary) are godsends