House Tokai is a small but long established noble family in the Butterfly Kingdom. The Tokai lands are on the northern tip of the kingdom, and were occasionally of import during wars of succession in repulsing attacks from the Shrouded Isle, but have otherwise played a minor role in the Kingdom's history. Several of the PCs may be related to it.
It is currently run by Tokai Wanakaru. A little over sixty, Wanakaru only ascended to control of the House about five years ago, on the death of his father, Hiakana, who was around 80. Hiroki and Hanako are probably descended from Hiakana, through one of Wanakaru's sisters.
Hiakana had three siblings. Two were about his age, Toranata and Kiyasa, and both left the Butterfly Kingdom to seek their fortunes elsewhere. Yoshi is descended from Toranata by way of Lin. The third, Takanata is more than twenty years younger, and played by Charles.
Recently, Song Min Feng has arrived at the Court from abroad and been taken on by Takanata as a ward. There is a modicum of gossip about this, as her arrival has not been explained to the court at large, but as neither Ti Lao nor Ti Wren seem disturbed by it, there has not been any great commotion.