A Marisa and Reimu couple refreshed during the winter. Knowing they have not enough food, Marisa tried aborting the baby when Reimu is asleep. She ate the baby and suck some of Reimu's filling, and liked it.
Later, Reimu is still sad and there's no more food. Marisa had an idea and refreshed again, wanting to eat more baby. But unlike previously, this time Reimu had baby inside her body.
By "accident" Marisa caused the baby to born prematurely, and then eat it when burying.
They then refreshed again, but this time Marisa is the mother. Marisa told Reimu to hunt for food in the winter or she will blame Reimu if their baby dies. Of course, Reimu can't find food and Marisa forcefully ejected the baby out.