軍靴をはいた猫

This is a world where "cat people" with animal ears and tails live.
Cats worship gods called "humans" as those "who would grant their wishes in return for overcoming the ordeals presented to them."

The abundant country where ruins and nature exist in harmony, the "Republic."
With the marriage of its princess, Tama, and her cousin Kotarou approaching,
the day of their "wedding ceremony" came, when they must inform the "humans" of their marriage.

Just as the ceremony was being carried out in solemnity, and was thought to end without any problems, in that moment,
a young man appeared along with a bright light.
He, with no animal ears nor tail, was none other than one of the "humans" that the cats revere.

And then, several days after the advent of the "human."
With the arrival of ships from the distant "Empire" from the other side of the sea,
the Republic, having spent their days in peace, now are faced with ordeals.
Thus the Republic and the Empire press forward into unrest, with both sides harboring their own feelings and intentions in their hearts, over "humans."

As the princess of a country,
as a single cat,
the decision that Tama makes is――

(translated from official site)