Winter is harsh for yukkuris, they have to have something to keep them warm, or they'll die. That's why they sometimes steal towels and such to pad their nests.
Anon comes across a family begging to be taken in, and gives them cookies. The koyukkuris are happy, and he talks to the mother Reimu, finding out that she was abandoned because she had kids.
He tells the kos that they should have had their easy place, instead of suffering in the elements. The mother understands his meaning: if she hadn't disobeyed her owner by having kos, they wouldn't be in this situation.
Because of that, she starts crying. The kos, not understanding, do their best to comfort their mother. But their words of kindness only wound the mother even more.
Anon thinks that this family will probably die over the winter, unable to procure padding, and dying in the cold.
"Reimu, you have such good little ones. Let them take it really easy, and raise them up well."
The kos promise their mother they will grow up well and let her take it easy, and the mother continues to cry. She knows they won't grow up, they won't live, because they'll die in the cold.
She understands, because she broke her promise with her owner, this happened. She might have been allowed to have children if she had just kept her word, and then those children would grow up to be nice and easy yukkuris.
Everything now is due to Reimu's fault. She can only cry and apologize.
Illustration: post #31982