This is from the wikipedia page for Japanese honorifics:
Heika is used for sovereign royalty, similar to "Majesty" in English. For example, Tennö Heika means "His Majesty the Emperor", which is used to address the Emperor of Japan, and Kögö Heika means "Her Majesty the Empress", used to address the Empress. Kokuö Heika means "His Majesty the King", and Joo Heika means "Her Majesty the Queen". Heika by itself can be used as a direct term of address, equivalent to "Your Majesty".
So in this case you could use either Tora no Joo or perhaps Tora Joo Heika?
The wikipedia page for Japanese names is also an interesting read.