This is the story of Jirōmaru, an akita puppy who lives in a small village in Ohu. Jiroumaru and his brothers, Saburōmaru and Tarōmaru and the sister Koyuki lived with their mother Yuki (Riki's granddaughter, Gin's niece) to their masters Yoshito Sawamura (an old prospector's gold) and Anju (Yoshito's granddaughter). One day, when Yoshito returning to the village with Yuki, he is bitten by a snake and falls into a ravine with the dog. Not seeing them return, Anju started to worry, however, she tries to take care of herself and the puppies. Yuki survives, but she is trapped in the ravine and as a way to get herself out from underneath a rock, she bites her own leg off and comes back to her home. Well there she collapse and tells Jiroumaru about what happened before she dies from her wounds.

Source: Ginga Wiki