You married while still a tourist
You came to Japan on a short visit, married while you were here, and would rather not leave. This is an extremely common situation and the answer is not the one most couples hope for.
Marrying while on a tourist entry is entirely lawful. What it does not do is shorten the immigration route. A change of status from 短期滞在 is only permitted where there are compelling special grounds, and the Agency states plainly that it is not normally allowed.
The expected path is that you leave Japan, your Japanese spouse files a Certificate of Eligibility application here, and you return on the visa issued against it. Your marriage is already registered, which means the hardest civil-law part is behind you and the 戸籍謄本 (family register) will show it.
The order things happen in
-
Obtain the family register copy showing the marriage before you leave
Useful to have in hand, and easier to get while you are both in Japan. -
Leave Japan within your permitted stay
Overstaying converts an ordinary case into a difficult one. Note that a short-stay entry carries no re-entry permission — leaving means a fresh entry next time. -
Your spouse files the Certificate of Eligibility application in Japan
No fee. One to three months. You are abroad while this happens. -
Collect the visa and return
At the mission covering where you live — you cannot apply for a visa from inside Japan.
Starts on the coe route, so you are only asked the questions that apply to this situation.