The Verdict: Need More Info
Nothing is available until the marriage is registered. Once you marry, report it so it is entered on your partner's Japanese family register (koseki), because every later application is built on that record.
A marriage held abroad is generally recognised, but it must be reported to a Japanese municipal office or consulate to appear on the register. A ceremony that is never reported leaves you unmarried on paper.
After that, two dates drive everything: the marriage and the day you start living in Japan. Naturalisation needs three years in Japan, or three years married plus one year in Japan. Permanent residence currently needs three years married and one year in Japan. A revision announced for 1 October 2026 would raise the spouse concession for permanent residence to five years of marriage and three years in Japan. We could not confirm it had been formally published, so check the current rule before you rely on the shorter one.
Japan gives no citizenship by marriage at any point, and naturalising means giving up your present nationality.