三千世界の子を殺し

Tomorrow night, the female head of their household, Hasumi, is to create a child with a man she meets for the first time, as decreed by the elders of their clan.
One time, she tried to escape this fate to the point of nearly dying. How will she spend her last day before that cursed yet promised night, with Yashiro— her chaperone— who once intervened with her attempt to die and saved her?

[Translated from the official website.]