[Nyororin]

Okay, I`m going to be rare and give the original poster the benefit of the doubt... As if I, at 28, can consider someone 15 one of my best friends... I guess I can`t say I am unable to imagine someone having enough in common with someone 8 years younger with them to end up in a relationship. (Although, just to be very clear, that is not happening in my case. I have better things to do than date middle schoolers...)

Let us say that you`re both mature and responsible... Obviously you are to some extent as you are researching things before jumping into this.

BUT - she is 16, and I doubt her English is THAT great... And it doesn`t look like your Japanese is either. (You asked for someone else to read the wiki article for you.) This leads me to believe that physical attraction, not "love" is the force at work here. Which would be fine, except that she`s 8 years younger than you. If the rush wears off, and she tells her parents, then they won`t be looking at the "law" and will jump on you for rape. In a normal case, (if you were Japanese) you MIGHT have a chance of defending yourself. But that`s pretty much out the window as you`re not.
Unless she is comfortable introducing you to her parents, then I would NOT go for sex. If it`s really *love* as you say, you should both be able to think maturely about the situation and realize things are far more likely to last and come to fruition if you hold back for a while.
Otherwise - what`s going to happen? You`ll have sex with her then leave Japan. Great end for your "real love" there. She can`t just up and marry you at this point - and if you have no interest in that outcome then it`s just a physical fling. Age has nothing to do with it on your side, but likely is making her think it`s true love.