Oyako Rankan The Animation

Story

Based on the eroge by Alice Soft. In a village, deep in the mountains off the beaten track, lies a house with a headman by the name of Kojiro. Secrets in this house have been ostensibly hidden. The village has been plagued by low birth rate for some time, and as a means to eliminate it, the village was provided with women from the Kamishiro family by the headman. This means was known as the "Feast." The protagonist, Mamoru, and his "onee-chan," Kotone, were the only survivors of a big fire ten years prior. Homeless, they were taken in by the Kamishiro family.

Synopsis via AniList (English).