Masao was one of the youngest pack mates of Kyoushiro's pack. When the Ohu army was heading towards Ohu to fight against the Great Dane Hougen, Masao, along with Teru and other young puppies of Kyoushiro's pack were left in the care of the old Koga ninja dog, Chourou. Masao and his friends grew up to be strong fighters and learned all the Koga ninja skills that Chourou had taught them. In the Hokkaido arc, Kyoushiro went back to the Koga territory to ask some advice from Chourou and he eventually bumps into his pack mates, in which he had left many months before. Kyoushiro then takes Masao and his friends to aid Weed's army in the attempt to defeat Victor and his Russian shepherd army.

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