No. It's not. He's not a minor is all that I am saying, so he's not being "groomed" or anything of that nature. He's been 17 the whole time.
I didn't say anything about it not being right or wrong. Just pointing out that he is of consenting age in Japan.
But, judging by your lack of punctuation and capitalization, I think it's obvious that you are the stupid one.
I see what you are trying to get at, and you are partially right.
While the age of consent is 16, meaning they can legally consent to sexual intercourse with an adult (18+), that does not mean they are legally an adult, nor would they be treated as an adult if a case were to arise.
16 is 16. They are still legally a minor. I do not know the exceptions to laws such as these in Japan, but it is safe to say that if Riku is consenting to this relationship then there should be no harm.
While it is distasteful to many, we are in no way in control of the story so…
I would like to mention though, Riku just graduated high school, meaning there is a very high possibility that he is now 18. While there has been no confirmation yet, there were many time skips, meaning his birthday *could* have possibly happened during that time.
The age of consent in Japan is 16, so Riku isn't a minor.