Ginko gets a letter from Shirasawa, the chief of a village. On silent snowy nights, when no sounds can be heard, many people go deaf in one or both ears. The doctors can't so anything, so they think it might be paranormal. Ginko looks into some of the villager's ears and he tells them that the cause is a Mushi called "Un". These Mushi consume the sounds that they hear. They usually live in the forest, but the snow is absorbing all the sound. He suspects that they came to the village looking for sound. He cures them by pouring salt water into their ears. He soon talks to Shirasawa and she tells him that there is one more person who has lost sound in both of his ears. Her very own grandson.
His condition is very different than the other people's. He has grown four horns on his head and can't hear anything at all. But he is able to hear strange sounds inside is head that he says are caused by the horns. Ginko believes it is the work of an "A". They are very rare compared to Un and they will work alongside the Un. There is only one attempt of somebody trying to cure it, and it didn't work. Will Ginko be able to cure Shirasawa's grandson?