The goal is to obtain the Great Moonlight, which is beneficial for the Kitsune Youkai's cultivation.
With unparalleled transformation abilities, the Killing Pillar replaced the then lord of Matsuyama Castle and stirred the hearts of people. Utilizing the convenience of being "the lord of the castle," he secretly summoned some Onmyoji and samurai to launch an attack on the Tanuki Clan.
It was unexpected that the Kitsune Clan of Matsuyama would suddenly assist the Tanuki Clan.
This led to the Killing Pillar tricking Inoue into the trap, followed by a series of subsequent events.
...
"Inoue Heitarō himself didn't even realize that he had sealed the Eight Hundred and Eight Tanukis along with the Great Moonlight. I've spent so much time, spent so long, just to regain control of these things; I'm just one step away, only one step away from advancing to become an Empty Fox."
The demon that once attacked Inoue was the Killing Pillar who had revealed its true form.
