"If you want to be formal it is King Tai, Tai-ou." He smiled softly, "But I don't think he minds, you can call him either. Though if you are worried you could ask what he would prefer."

People used personal names, rather than family names more often in his own world than they did in Japan. It might have been because of how families were different, with children being born on the riboku and such things like inheritance not being lawful.

But it's not something he really knows, one of those things that... As a Taika he will always not be too sure of. In the palace most people were called by their titles, rather than their names.