Extending Tourist visum for 2 weeks

Since I will be on my second tourist visum from januari until march, I would like to stay a bit longer so I can go to a friends' wedding. The leaving date would be postponed to somewhere around two weeks after my visum would expire, but in the worst case any extension as little as a week would be welcome. I've been reading up on the internet and have read mixed stories about whether this is possible. Anyone that can share more info? Also, if I changed my story a bit would that increase my chances? I could say I need to take a test in school but I'm afraid they will want to check my papers, which I can't provide.. I'm really desperate for a solution, as I would like to stay just that little bit longer.

Anyone know anything about if this is possible?

John,

It is possible for citizens of certain countries (e.g. UK) to extend tourist visas by 3 months, but are you saying that you want to extend a second time beyond that?
I don't think that is possible except in dire emergencies, but you have nothing to lose by asking Immigration. Another option would be to leave the country briefly and return for the wedding.

Don't say you need to take a test in school- if you are studying and need longer than 90 days Immigration would expect you to have a student visa.

As Dave says, extensions are not often given. Flying or taking a ferry to Korea for a day or two is one option although it's not guaranteed you will be allowed back into Japan.