You are already in Japan on a work or student status and have married

You hold Engineer, Student, Dependent or a similar status, you have married a Japanese national, and you want to switch to the spouse status — usually because it removes the restriction on what work you may do.

You do not have to change. Your existing status remains valid until it expires, and if it suits you there is no obligation to switch. People do switch because the spouse status carries no work restriction at all.

The critical procedural point: you must attend the immigration office yourself. There is no representative on this route. Your Japanese spouse is your guarantor, and may come with you, but cannot file for you — and cannot file online on your behalf either. Only an accredited lawyer or 行政書士 (administrative scrivener) acting as a filing agent, or a legal representative, can go instead.

The order things happen in

1. Register the marriage and obtain the family register copy
   Your municipal office will want a certificate of legal capacity to marry from your own country's embassy, with a Japanese translation naming the translator.
2. Update your residence record
   Obtain a 住民票 (certificate of residence) showing the whole household, with 続柄 (relationship to the head of household) and 本籍 (registered domicile) included — they are omitted by default unless you ask.
3. Assemble income evidence for the household
   Your spouse's 課税証明書 (taxable income certificate) and 納税証明書 (tax payment certificate). If either of you changed jobs recently, add an employment certificate — the tax certificate will still show the old salary.
4. Attend the immigration office and file
   At the bureau covering your registered address, before your current status expires. 6,000 yen on permission, or 5,500 yen if you file online yourself. Standard processing period one to two months.

Starts on the change route, so you are only asked the questions that apply to this situation.