A quick question,
Are Foreigners protected by law if they need to defend themselves against an assault from a Japanese person or another foreigner, and/or protect another person from an assault?

Will it simply be viewed as fighting and the verdict be against the foreigner who defended themselves?

Although it is highly unlikely that a Foreigner who is respectful of the culture and the law will get into a fight while they are in japan, it can be possible to be in the wrong place at the wrong time. With a chance that you may not be able to run anywhere and might end up backed into a corner, even after you have tried to reason with them in a calm and discrete manner.
Also with foreigners having a bad reputation for violence, some witnesses could assume the foreigner provoked the attack.
What would be the probable outcome if this happened?

I don't know which country you are living in now, but if you don't get in to fights there, you wont get into fights here.
These people are not like that.
And if you don't hang out with foreign idiots, you will be fine.
Our "man on the scene" has made videos about this in his "how to" play list.

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Japanese police are like every other police force in the world and should treat everyone fairly. That said, I think they have a biased opinion favoring other Japanese. If you're not looking for trouble, you should have no problems in Japan. Japanese people, tend to go out of their way to avoid conflict and even when they're drunk, they're more jovial than violent. I'd sometimes walk home from a late night out in Osaka or Tokyo, after the trains had shut down, and never once felt my safety was in jeopardy.

2010 and men around the world are still beating their chests and waving clubs in the air
Civilization is yet to evolve..

Fortunately, Japan society seems to be the least violent of the countries I have been to.

hi there..

I was only for vacation/sightseeing in japan but I don't think you will have to defend against anyone there.. people are very friendly and everything.. I was there for only two weeks but still.. I don't think you should care about getting into fights.. As mentioned above: idiots are everywhere..