Kuchi ga Mimi made Sakeru Toki

Sakura's family is poor, so she is adopted by a new family constituted of a mother and a grandmother. Sakura new mother's skin is strangely cold, her mouth is sometime splits open and her neck seems to be stretched.
As she gets used to live with her new family, Sakura discovers that a girl was adopted before her about a year ago, but she then disappeared last winter.