Cool is Wolf's closest minion and right hand.
Cool was one of the four dogs belonging to Wolf's rogue group which attacked the peaceful local pack of Gunma Prefecture. He obeyed Wolf's every order and helped him to slaughter local dogs and get females for him.
Later, Cool is seen with Wolf and the other minions when Toki shows up. Toki tricks most of the minions away, including Cool, by telling them that he has hunted a wild boar like he was ordered to but it's too heavy for him to move alone.
Cool isn't seen again but it's mentioned that he was beaten and driven away after Wolf's death.