Reto the Protector

From Manga UP:
Clad in a blood-soaked coat and with no destination in mind, a young boy named Reto wanders into an Ainu village amidst a blizzard, whose residents provide him with much-needed shelter. All he has are two things: the memory of his mother dying before his eyes, and an ancient hunting knife without a blade.

Reto the Protector, Otogi no Hako no Reto , お伽の匣のレト