Might as well throw something on this train to rebalance it for a little longer before it inevitably derails.
I know the Kyuubi/Nine tailed fox has been mentioned already, but it would be interesting. Given the protector-of-royal-blood thing, something like "Dynast Kyuubei" or similar.
The 'bei' spelling is really just a pun on 'beyblade', but perhaps something more creative could be done to work in the name of a notable member of royalty that had some association with the ninetails. I would consider something like Bao Si or whatever, but that would largely counteract the "dynast" idea based on the mythos (yay wikipedia).
Dynast is just there for the obvious related meaning and because it sounds nice to me. It also sounds somewhat realistic, to me, at least.