I dont know which era it was, but an emperor went on a state visit to China and came back with a wife. In those days really there was no such thing as wife, so a consort of high rank. Prior to that time the Emperors believed they had some choice in the their lovelives. He was promptly informed this wasnt true.
The woman was given high rank but another woman was made empress and a family formed to insure that such a situation as a forign emprial consort never arose to unseat them.
In time this woman had many children, and among her descendants by the emperor were chosen women to inherit her position as well.
These women later became empresses and mothers of emperors. They also were supposed to send sons back to china to bring over more women like themselves, but doing so diminished the chances of their sons becoming emperor, and they usually had a pretty good chance otherwise.
The young man who "studdied the wrong religion" was one of those princes, and had his mother not overloaded his head to make him look incompetant enough that he would be allowed to sneak off to China and get a wife, he would have been emperor easily.
He founded the families who got permission to live off shore and in Samurai hierachy direct descent from emperial princes ranks a family pretty high.
This fact was neglected when the order to return was sent out.
