Kamakurako (かまくら子, "Igloo child"), is a character in Madotsuki's dream world. She's in a deep sleep in an igloo to the southeast of the entrance to the Snow World.
She has brown hair, wears a gray shirt and black bottoms and closely resembles a younger version of Madotsuki with her hair let down. Although it seems that nothing can break Kamakurako out of her deep sleep (besides killing her), she seems to react when Madotsuki meows when using the cat effect with a small tremble. Whether she is shaking from fear or from the cold is up to fan speculation.
Note: the word "Kamakura" refers to the Kamakura festivals of northern Japan where child play house in little snow huts (References: [1] [2] [3]). However, it is used in Japan as a generic word for "igloo" since Japanese does not actually have a word for "igloo" (other than the English loanword).
Fan Speculation
Little can be said about Kamakurako due to the limited action she provides. It could be possible that she has a fear of cats considering their sound is the only thing she reacts to.
It is also possible that she is a younger version of Madotsuki when compared to Madotsuki when she's sleeping with long hair (Kamakurako's hair is slightly shorter than Madotsuki's).