Kyūbi no kitsune are very old and powerful yokai being at least 9,000 years old. Physically, the kyubi stand out for their larger size and their nine long tails. When a kitsune gains their ninth tail, their fur turns silver or gold and their mastery over fire and shadow magic is greatly increased. These capricious beings are almost worshiped as minor deities by the people of Nippon and it makes sense for they are ancestral beings that precede even the great catastrophe and have thus gained unparalleled wisdom and knowledge over time.
You can learn more about the Nippon the Oni shogunate fan project here: https://www.worldanvil.com/w/warhammer-fan-concept3A-nippon-the-oni-shogunate-danilagi7