[buzer]

I assume they mean: Given turning/waiting car A, passing car B that is going straight and car C coming from right going straight. Car B likely has right of the way as they are going straight and they are on the left from viewpoint of car C, but car C may not see behind car A (like due to it being truck for example). Both B & C might think they have right of the way. B due to fact they should normally only need to avoid people coming from left and he can see there is no one there, C due to fact he entered intersection when he only saw A who is waiting to turn. I don't know Japan law so I don't know actually has right of the way here (in Finland A would actually have right of the way in mirrored situation as you always need to yield those coming from right in equal intersection, even if they are turning left).

[pezezin]

Yes, it is a question of visibility. You have two cars coming from opposite directions, both want to turn right (Japan drives on the left), and both think they can do it safely, but all of sudden another car pops from behind.

I have seen many near accidents due to this. That's why such a maneuver is forbidden in many countries.