The Guardian is one of the few members left from a noble clan sworn to protect Shenkuu and the Empire's citizens. In the past she has prevented the Emperor's assassination by having him switch places with his third cousin, stopped a traitorous guard from taking the throne, and caught a Wocky thief who was stealing documents from the palace. She is always watching, to keep the peace.
Long have I guarded Shenkuu and its citizens from harm. Though it is not common knowledge, an emissary of the Emperor is aboard this ship, and so I must travel with it to ensure that he comes to his destination alive and unharmed. Forgive my bluntness, but I doubt you can do any better than I, as you lack my training.
The Guardian appeared in issue #26.