臼石店長 (Usu-ishi Tenchou, Quernstone Manager) is an original character created by Yagisaka Seto as a manager of the school store in Pixiv Gakuen project.
His original name is Gemma Agamas Boltac, but everybody calls him this nickname.
He is originally male, however his Genderswap version is sometimes drawn.
He has light Purple Hair, blue/purple heterochromatic eyes, a Monocle, hair-like Fox Ears, Fang and eight Fox Tails.