The manga tells a fictional version of the story of historical Tang China diplomat Wang Xuance, centering on his diplomatic journey from Tang Dynasty China to the Empire of Harsha in India in the 7th century CE. When he comes upon a crumbling empire that is now hostile to him he escapes to Tibet and raises a confederation of Tang, Nepalese, and Tibetan soldiers to mount a raid on the Empire of Harsha.

From CMX:
Kasche may have a talent for controlling beasts, but she's got a lot to learn about self-control before she can become a full-fledged summoner. When disaster strikes, her principal chooses her to avert it.
Joined by an unusual crew of allies both human and not, Kasche must recapture the relic from an evil summoner before she can use it to unlock the ancient Encyclopedia Verum and call up the most powerful monsters ever seen!

Tokugawa, the ruler of Japan wants to keep Japan isolated from the rest of the world, however there are those who oppose this decision and plot to usurp Tokugawa's authority. It's the job of one of Tokugawa's bodyguards to stop these evil plots.