The Almighty dF
Pharaoh
The only one issue I have with giving Japan a Seafaring leader, now that I have read up on all of them a little bit (well just Wikipedia), is that there is really no basis to give it to any of them really. If anything maybe Meiji actually. There is really no reason to give it to Jingu or Tokugawa. And Hirohito could really have any traits almost, I mean he did reign for a long time, and on top of that he is more or less there to represent Japan rather than himself if that makese sense.
Jingu -did-, allegedly, lead a naval and land invasion of Korea.
Again though, since Jingu's only really known for one thing (which even Japan doesn't believe happend since there is no evidence supporting Japan ever controlled Korea at that time), it's kinda hard to give her traits period.
That's why for Jingu I'd vote Seafaring (in-part naval invasion of a foreign nation) combined with a trait to show off her alleged rule of Korea (Org, Imp, Exp)