A. Immediately, you must go to the Immigration Bureau.

Although there is no description in the law, "special acceptance" may be accepted as practical usage.

This is done as a remedy to foreigners who could not apply for extension due to various circumstances up to the period of the visa.

Of course, there is no provision in the law, so it can not be said whether special acceptance will be accepted or not 100%.
But there are also many foreigners who have been specially accepted.

If possible, you should apply for an extension of the visa before three months of the period.

However, if you carelessly do not apply the extension, you must go to the immigration office immediately.
The shorter the time passed from the period of your visa, the better situation is, so immediate action is necessary.

Of course, consulting an immigration lawyer and go there together is also a very effective hand.