Made in Abyss: Retsujitsu no Ougonkyou

Synopsis

Vueko begins to recount her time with Ganja after arriving at the Sixth Layer. Realizing that they cannot return to the surface, they resolve themselves to survive in this new environment. Vueko establishes a parent-like connection with the young tribe girl, named Irumyuui, who tells her that she was deemed a curse by her family for being infertile, leading to her exile. With time, the Ganja successfully find a water source and learn the means to survive in the Sixth Layer, living comfortably in their new home. However one day, Vueko finds Irumyuui and several Ganja severely sick. While fetching more water, Wazukyan finds the food survey team dead and deformed, with a small egg-like object in their possession. Soon after, they learn to their horror the water they were drinking was actually a parasitic organism that reproduces upon intake, and that time is short for them to find a cure. They also identify the egg-like object as the Cradle of Desire, a Relic that can grant "the deepest of wishes", though complex ones will result in the deformation of the individual, thus its resonance is stronger with children. As the pseudowater takes further effect on Irumyuui, the Sages agree to give her the Cradle, hoping that her wish will save them all. Irumyuui wakes up better, but her body begins to deform further with time. Then one day, Irumyuui gives birth to a small creature, leading Vueko to realize her wish was to have children. However, the creature is born without internal organs and dies soon after. Irumyuui continues to regularly birth and lose her children by the day, bringing her immense grief. Eventually, Vueko finds herself succumbing to the psuedowater, but Wazukyan feeds her a mysterious broth that miraculously heals her. When he states that Irumyuui really did save them all, Vueko realizes to her horror that she had just eaten Irumyuui's dead children.

(Source: Wikipedia)