Not required, but transformative. Italki tutors run $15–$30/hour for conversational practice in most languages; group classes at local language schools are often $100–$200/month for daily sessions. In our experience, even 30 minutes of daily study in the first month of a stay shifts the quality of daily life significantly — not because you achieve fluency, but because attempting the language changes your relationship to the neighborhood.
For Japanese specifically: even learning the two phonetic alphabets (hiragana and katakana) before arrival makes Yanaka significantly more legible. For Portuguese: the grammar is genuinely learnable in a month of daily effort, and Lisboetas respond to the attempt with disproportionate warmth.