[spicytuna]

That's a good question. Did you ever have a Japanese passport?

It's obviously a grey area since the Japanese govt doesn't allow dual citizenship. With that being said, I know dozens of Japanese Canadian who have 2 passports and are currently living in Japan. However, in their case, they all had a Japanese passport long before they turned 18.

Is there a reason you'd want to become a Japanese citizen? Are you planning on living there permanently?

As you probably know, you should be able to qualify for the "Child of a Japanese national" visa.