wait for him to transform the chikage, and go ham on the son of a *****. he won't be able to parry, and if you have a fast weapon, he will be stunlocked for a bit, and he will take damage over time because of the transformation. If he doesn't do that, parry his running attack. try to use numbing mist as much as possible before he uses his blood vial, but him using it eventually is inevitable. watch out fo his gun, its more dangerous than his chikage.