An old family rooted in Fuyuki since the Tenshō (1573~1592) era. When one thinks that it was there since about the time Nobbu was burnt or not, it’s a lineage with quite the history.
The Sakatsuki family were wealthy farmers that were allowed the right to bear a surname and a katana. It was during the time of the third generation that the strange phenomenon was seen.
Total annihilation of the rice fields due to a record-setting flood. It lasted for several years. The dead by starvation continued appearing one after another, and the decline of labor force resulted in a further reduction of the harvested amount. The chain of poverty was already in an unstoppable state. Corpses and resignation were widespread around the land, and on top of that snow fell and accumulated mercilessly. That late winter in which every hope was given up, a child was born at the Sakatsuki family.
―It was a baby girl that had red eyes.

That year, Fuyuki was struck by a strange abundant harvest. The sun was shining, the earth grew fertile, and the river was full of gentle currents. The natural disaster took a sudden change and was turned inside out into a gift of nature. The destiny of people is so influenced by the whims of nature. When the object of fear and gratitude is replaced to something else that is not nature, the concept of Mystery is adhered.

The farmers regarded the baby girl of the Sakatsuki family as “a child sent by the god of fertility,” and revered her. A narrow and deep faith was fervently consecrated to the red-eyed baby girl, and she actually brought harvest until two years later. And the baby girl died without counting her third year.
Whether the red-eyed baby girl really had the power of Mystery or not can’t be ascertained after all this time. If Mystery gave birth to faith or if faith gave birth to Mystery isn’t important. Because after that, the baby girls born in the Sakatsuki family had all red eyes, and undoubtedly possessed a paranormal power ― the property of granting the wishes of people.

Since then, the Sakatsuki family spent several generations learning the way of treating the God Child. If that power was well used , harvest, prosperity, and even execution of criminals could be done as one pleased. But the conclusion they got was “not to use the power of the God Child.” While omnipotent power was in their hands, they renounced to their right to use it. That decision was made out of a modest and deep affection towards the child.
Well, with something like that, the Sakatsuki arrived to the present as an old family of women, without having prospered, without having been ruined, for generations. Infant girls from the Sakatsuki family generally are not different from ordinary girls after they surpass the age of six. But, maybe as an after-effect of the mother’s wish of “raising them healthily,” in general they are raised to become superwomen with excessively high specs in both mind and body. Such a lady of character played an active role in rain or shine, and sustained the house.

PRISMA material/petit: Encyclopedia of Prisma Illya MOVIE