Sayuri

Sayuri is half kitsune/half oni demon (mother was powerful kitsune goddess, father was king of the onis.)

She was raised with her mother, due to oni children going 'savage' when they turn 18, learning how to kill/fight, and her mother wished for her to be raised away from that.

When she was younger, her horns were smaller and covered by her hair and ear fur.

As she grew older and reached the age of 18, her horns began to show, and her mother, fearing for her daughter's life quality, sent her away to the human world.

Her ears are able to be hidden using her kitsune illusions, but on the 11th of every month, her ears + horns + 3 tails emerge and she is unable to hide them.