Kurohabaki Masamune is the main antagonist of GDW:O. He is a ninja dog, the leader of the Kurohabaki Clan. He is the adopted son of Kurohabaki Terumune and Yamabiko's big brother. It is unknown which breed he is.

In GDW:O,  he was still just a pup, Masamune's owner, Kurohabaki Jinemon, gouged his eye out and left him in the mountains to die.Luckily, Terumune, the Kurohabaki Clan Leader, finds him and adopts as his own son. Then, his younger brother Yamabiko was born. Terumune looked after Yamabiko more than Masamune and had already decided that his son shall succeed him to obtain the leadership of the clan. This made Masamune angry and thirst for revenge. He then banished his father and took the leadership of the clan. But his revenge wasn't accomplished, for he had to kill his younger brother, who was sent to Shikoku to avoid battle. After the volcanic eruption in Ohu, he takes over the utopia and convinces other dogs from nearby areas to join and strengthen his huge army of Kai-Kens.