Income, and what to do if it is low

There is no statutory minimum. The test is whether the household can live in Japan without recourse to public assistance.

If the income is modest, the answer is not to inflate it -- the 課税証明書 (taxable income certificate) states the real figure and the form is compared against it. The answer is to widen the evidence: savings balances, the fact that housing is owned or provided by family, a job offer with a start date, a second earner, or a parent formally acting as supporter at item 25 of the application.

Recent job changes are worth explaining rather than leaving to be noticed. A spouse who changed employers three months ago will have a tax certificate showing the old salary; an employment certificate and a recent payslip close that gap.

If the Japanese spouse is not working at all, say so plainly and show how the household is funded. An honest 無職 supported by savings evidence is treated far more sympathetically than an occupation that the tax records do not support.